Compounds having a potentiating effect on the activity of ethionamide and uses thereof

ABSTRACT

The present invention relates to the use of compounds with a potentiating effect on the activity of antibiotics that are activatable via the EthA enzymatic pathway, for the preparation of a medicament for preventing and/or treating mycobacterial infections such as tuberculosis and leprosy, to pharmaceutical compositions comprising them in combination with an antibiotic that is activatable via the EthA pathway, to compounds having a potentiating effect on the activity of antibiotics that are activatable via the EthA enzymatic pathway, to pharmaceutical compositions comprising them and to their use as medicaments, especially medicaments for preventing and/or treating mycobacterial infections such as tuberculosis and leprosy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage application filed under 35 U.S.C. 371 of International Application No. PCT/FR2007/001138, filed Jul. 4, 2007, which claims priority from French Application No. 06/06088, filed Jul. 4, 2006.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to the use of compounds with a potentiating effect on the activity of antibiotics that are activatable via the EthA enzymatic pathway, for the preparation of a medicament for preventing and/or treating mycobacterial infections such as tuberculosis and leprosy, to pharmaceutical compositions comprising them in combination with an antibiotic that is activatable via the EthA pathway, to compounds having a potentiating effect on the activity of antibiotics that are activatable via the EthA enzymatic pathway, to pharmaceutical compositions comprising them and to their use as medicaments, especially medicaments for preventing and/or treating mycobacterial infections such as tuberculosis and leprosy.

Tuberculosis kills two million people per year worldwide. The AIDS epidemic and the emergence of antibiotic multiresistant strains have contributed toward worsening the impact of this disease, which is considered by the World Health Organization as being responsible for an increasingly dangerous worldwide epidemic, and as being a worldwide health emergency. The WHO estimates that, between 2000 and 2020, close to one billion people will be infected with the tuberculosis bacillus and about 200 million of them will develop the disease, which may lead to the death of 35 million people if no improvements are made in controlling or treating this infection.

An increasing number of Mycobacterium tuberculosis strains are characterized at the present time by multidrug resistance to the first-line antibiotics isoniazid (INH) and rifampicin (RIF). These antibiotics have a high therapeutic index (the therapeutic index of an active principle is the ratio of the therapeutic dose to the toxic dose) and should thus be replaced with second-line antibiotics to which the strains are not resistant, but which have the drawback of having a lower therapeutic index.

Among these second-line antibiotics, ethionamide(2-ethyl thioisonicotinamide: ETH, Trescatyl; CAS number 536-33-4) has been commonly used clinically for more than 35 years mainly in the treatment of pulmonary and extrapulmonary tuberculoses (Mycobacterium tuberculosis), and secondarily for treating infections with atypical mycobacteria (Mycobacterium kansasii) and leprosy (Mycobacterium leprae). ETH is a prodrug that needs to be activated in order for its antibacterial activity to be able to be exerted. The activation of ethionamide is performed by a specific mycobacterial enzyme, the enzyme EthA, which is a flavin monooxygenase of Baeyer-Villiger type. In its normal physiological state, the mycobacterium synthesizes little EthA enzyme, which limits the activation of the prodrug and is reflected by low sensitivity of the bacterium toward this antibiotic. Recently, the mechanism of expression of the gene encoding EthA was elucidated by Baulard et al. (Baulard A. et al., J. Biol. Chem., 2000, 275(36) 28326-28331) and Engohang-Ndong et al. (Engohang-Ndong et al., Mol. Microbiology, 2004, 51(1), 175-188). Expression of the ethA gene is placed under the control of an adjacent gene: the ethR gene. The ethR gene encodes a protein, EthR, which binds to a target DNA sequence upstream of the ethA gene sequence. On binding to the ethA gene promoter, the EthR protein acts as a transcription repressor for this gene. By genetically inactivating the ethR gene, hypersensitivity of the mycobacterium to ethionamide is observed (Baulard et al., 2000, cited previously; Engohang-Ndong et al., 2004, cited previously), due to the non-repression of ethA transcription.

ETH is an antibiotic that is known to greatly inhibit the biosynthesis of mycolic acids, which are essential constituents of the mycobacterial wall. Its presumed target is the enzyme enoyl-AcpM reductase (InhA). Its administration in therapeutically effective doses, generally 10 mg/kg/day (Johnson et al., J. Pharm. Pharmacol., 1967, 19, 1-9) leads, however, to adverse side effects such as liver toxicity, mental impairment (psychoses, anxiety, depression), intestinal disorders, and ocular and auditive impairment (Reynolds J E F et al., 1989, Martindale, the extra pharmacopoeia, 29^(th) ed. London, The Pharmaceutical Press, 562-563). Its use is, however, common in developing countries for the treatment of patients who relapse as a result of infection with strains of M. tuberculosis that are resistant to first-line antibiotics, or for treating patients suffering from lepromatous leprosy, as a replacement for clofazimine.

There is therefore a certain advantage in developing a technical solution for reducing the dose of ETH, and thereby its adverse side effects, while at the same time maintaining or improving its therapeutic efficacy.

With this aim, it has already been envisioned to potentiate the activity of ETH by combining it with a particular compound. Thus, international patent application WO 2005/047 538 describes a process for identifying EthR repressor inhibitors, and also chemical compounds having this effect. Said patent application cites, various compounds in this respect, among which is especially hexadecyl octanoate. The activity of this compound was also studied in the article by Frénois F. et al., Molecular Cell, 2004, 16, 301-307. However, given the length of its carbon chain, hexadecyl octanoate is a compound having very low bioavailability. Moreover, it is not active on live mycobacteria.

In addition, the pathway for activation of the prodrugs by EthA has also been recently illustrated for thiacetazone (Qian L, et al., Chem. Res. Toxicol. 2006, 19, 443-449), and indirectly for isoxyl (DeBarber A E, et al., Proc. Natl. Acad. Sci. USA, 2000, 97, 9677-82). Any compound capable of interfering with the EthA activation pathway should thus allow the action of these prodrugs to be potentiated.

The Inventors thus set themselves the aim of providing compounds that are easier to formulate than hexadecyl octanoate and that can be used in combination with ETH in order to potentiate its activity. This type of medicament might contain, in addition to the compounds forming the subject of the present invention, smaller doses of ETH, while at the same time maintaining efficacy that is at least equivalent to that of a medicament containing only ETH.

SUMMARY OF THE INVENTION

This objective is achieved by the compounds of formula (I) that will be described hereinbelow, and that may be used for preventing and/or treating bacterial and preferably mycobacterial infections.

A first subject of the present invention is thus the use of at least one compound of formula (I) below: A-L-B  (I)

in which:

-   -   the unit A is connected to L via at least one covalent bond and         is chosen from the groups of formula (II) below:

in which:

-   -   the arrow indicates the point of attachment of the covalent bond         connecting X₁ to L, said bond involving at least one carbon atom         of the group X₁ and a carbon, nitrogen or oxygen atom of the         group L,     -   n is an integer equal to 0 or 1,     -   when n=1, X₁ represents a group chosen from C₂-C₅ alkyl chains;         it being understood that a carbon atom of the group X₁ is         engaged in the covalent bond connecting X₁ to —NH—,     -   when n=0, X₁ represents a cyclic mononitrogen or dinitrogen         group chosen from piperidine, piperazine, pyrrolidine and         tetrahydropyridine, it being understood that the covalent bond         connecting X₁ to X₂ involves a ring nitrogen atom of the group         X₁;     -   X₂ is chosen from the groups of formulae (IIIa) to (IIIc) below:

in which:

-   -   the arrow indicates the point of attachment of the covalent bond         between X₂ and —NH— when n=1 or between X₂ and X₁ when n=0,     -   X₃ is O or S,     -   Y represents a group -(T)_(p)-(CH₂)_(m)—R₁ in which:         -   p and m, independently of each other, are integers equal to             0 or 1;         -   T is chosen from O, NH and CH₂; and         -   R₁ is chosen from a hydrogen atom; a linear or branched             C₂-C₄ alkyl radical; a linear or branched C₂-C₄ haloalkyl             radical; a C₂-C₄ alkene radical; a C₂-C₄ alkyne radical; a             linear or branched C₂-C₄ alkoxy radical; a             (C₂-C₄)alkylcarboxylic group; a cyano group; a saturated or             unsaturated C₃-C₆ hydrocarbon-based radical optionally             substituted with a C₁-C₄ alkyl radical or with a methylene             bridge; an azido group; a benzyloxy group; an aromatic or             heteroaromatic ring optionally substituted with one or more             substituents chosen from a halogen atom and an amino, linear             or branched C₁-C₄ alkyl, C₁-C₄ alkoxy or cyano group; or a             triazole ring which is unsubstituted or substituted, in             position 4, with a trimethylsilyl group or a group chosen             from the compounds of formula (IV) below:

in which:

-   -   the arrow represents the point of attachment of the compound of         formula (IV) to X₂ via a covalent bond,     -   R₂ and R₃, which may be identical or different, represent a         hydrogen atom, a halogen atom preferably chosen from chlorine,         iodine and fluorine, a C₁-C₄ alkyl group or a nitro group; when         R₂ and R₃ are adjacent, they may also form a methylenedioxy         group or, together with the carbon atoms of the benzene ring on         which they are borne, a 6-membered carbon-based or         heterocarbon-based ring, said ring being optionally substituted         with a di(C₁-C₄)alkylamino radical or a trifluoroacetyl radical;     -   the unit B is connected to L via at least one covalent bond and         is chosen from aromatic hydrocarbon-based rings, polyaromatic         hydrocarbon-based rings, monocyclic heteroaromatic rings         containing at least one heteroatom chosen from S, O and N,         saturated or unsaturated C₃-C₇ hydrocarbon-based rings,         saturated or unsaturated C₃-C₇ heterocycles, and a         benzothiazolyl group; said rings and said group possibly being         unsubstituted or substituted with one or more substituents         chosen from halogen atoms, linear or branched C₁-C₄ alkyl         radicals, linear or branched C₁-C₄ alkoxy radicals, a         methylenedioxy group, linear or branched C₁-C₄ haloalkyl         radicals, linear or branched C₁-C₄ haloalkyloxy radicals and an         amino group which is unsubstituted or substituted with one or         two benzyl groups;     -   L represents a group that provides the bond between the two         units A and B and is chosen from unsaturated 5-membered         heterocycles comprising from 1 to 4 heteroatoms chosen from N, O         and S,

it being understood that when R₁ represents a linear or branched C₂-C₄ alkyloxy group and when p=1, then T is chosen from NH and CH₂;

for the manufacture of a medicament for preventing and/or treating bacterial and preferably mycobacterial infections.

According to the invention, the following definitions apply:

-   -   aromatic ring: any flat ring compound with conjugated pi bonds,         in which each ring atom comprises a p orbital, said p orbitals         overlapping,     -   polyaromatic ring: any cyclic compound resulting from the fusion         of at least two aromatic rings as defined above.     -   halogen atom: any bromine, chlorine, fluorine or iodine atom.

When n=1 and when X₁ represents a C₂-C₅ alkyl chain, this chain is preferably chosen from ethane, propane, butane and pentane chains.

When X₂ represents a group of formula (IIIa), this group is then preferably a group in which X₃ represents O, Y represents a group -(T)_(p)-(CH₂)_(m)—R₁ in which p=0, m=1 and R₁ represents an azido or thiophenyl group that is unsubstituted or substituted with one or more halogen atoms.

Among the groups of formula (II) hereinabove, mention may be made of those in which:

-   -   n=1, X₁ represents a C₂-C₅ alkyl chain and X₂ represents a group         of formula (IIIa), in which X₃ represents O or S, Y is a group         -(T)_(p)-(CH₂)_(m)—R₁ in which p=1 and T represents an oxygen         atom, m=1 and R₁ represents a linear or branched C₂-C₄ alkyl         radical;     -   n=0, X₁ represents piperidine or pyrrolidine and X₂ represents a         group of formula (IIIa) in which X₃ represents O or S, Y is a         group -(T)_(p)-(CH₂)_(m)—R₁ in which p=1 and T represents an         oxygen atom, m=0 and R₁ represents a linear or branched C₂-C₄         alkyl radical;     -   n=0, X₁ represents piperidine or piperazine and X₂ represents a         group of formula (IIIa) in which X₃ represents O or S, Y is a         group -(T)_(p)-(CH₂)_(m)—R₁ in which p=0, m=1 and R₁ represents         an azido group, a cyano group or a heteroaromatic ring,         preferably thiophene or triazole;     -   n=0, X₁ represents piperidine or piperazine and X₂ represents a         group of formula (IIIa) in which X₃ represents O or S, Y is a         group -(T)_(p)-(CH₂)_(m)—R₁ in which p=0 or 1 with T=CH₂, m=1         and R₁ represents a saturated C₃-C₇ hydrocarbon-based ring;     -   n=0, X₁ represents piperidine or piperazine and X₂ represents a         group of formula (IIIa) in which X₃ represents O or S, Y is a         group -(T)_(p)-(CH₂)_(m)—R₁ in which p=0, m=0 and R₁ represents         a t-butyloxy radical or a benzyloxy group;     -   n=0, X₁ represents piperidine or piperazine, and X₂ represents a         group of formula (IIIa) in which X₃ represents O or S, Y is a         group -(T)_(p)-(CH₂)_(m)—R₁ in which p=0 or 1, m=1 and R₁         represents a triazole ring substituted with a compound of         formula (IV) in which:

i) R₂ and R₃ represent a hydrogen atom,

ii) R₂ represents a hydrogen atom and R₃ represents a halogen atom or a methyl radical, preferably in the para position relative to the sulfonamide function,

iii) R₂ represents a nitro group in the ortho or meta position relative to the sulfonamide function and R₃, in the para position relative to the sulfonamide function, represents a hydrogen or halogen atom;

iv) R₂ and R₃, in the ortho and meta positions, form a benzene ring optionally substituted with a dimethylamino group;

v) R₂ and R₃, in the meta and para positions, form a piperidino ring in which the nitrogen atom is substituted with a trifluoroacetyl radical.

When the unit B is an aromatic hydrocarbon-based ring, said ring is preferably chosen from phenyl and phenyl substituted with one or more halogen atoms and/or one or more groups chosen from methyl, t-butyl, trifluoromethyl, trifluoromethyloxy, methyloxy, dibenzylamino and methylenedioxy groups.

When the unit B is a heterocycle, said ring is preferably chosen from thiophene, furan, 2-pyridine, aminothiazole and benzothiazole rings.

When the unit B is a saturated hydrocarbon-based ring, it preferably represents a cyclopropane.

According to the invention, the unit B is preferably chosen from phenyl, thiophenyl, furyl, 2 amino-(1-3)thiazol-5-yl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 4′-t-butylphenyl, 4′-trifluoromethylphenyl, 2′,3′-methylenedioxyphenyl, 4′-fluorophenyl, 2′-methyl-3′-chlorophenyl, 2′-trifluoromethyl-5′-fluorophenyl, 2′-trifluoromethyloxyphenyl, 2′,5′-difluorophenyl, 2′-chlorophenyl, 2′-methyl-oxyphenyl, cyclopropanyl and benzothiazolyl groups.

According to one particularly preferred embodiment of the invention, the unit B is chosen from thiophenyl, phenyl, fluorophenyl, aminothiazolyl, benzothiazolyl and 2-pyridyl groups.

According to the invention, when L represents an unsaturated 5-membered heterocycle, it is preferably chosen from oxadiazole, triazole, isoxazole, imidazole, thiadiazole, pyrrole, tetrazole, furan, thiophene, pyrazole and thiazole rings.

As compounds of formula (I) used in accordance with the invention, mention may be made in particular of:

a) the compounds corresponding to formula (I-a) below:

in which the unit B is chosen from the groups of formulae (B-1) to (B-21) below:

b) the compounds corresponding to formula (I-b) below:

in which X₁ is chosen from the groups of formulae (X₁-1) to (X₁-4) below:

c) the compounds corresponding to formula (I-c) below:

in which X₁ is chosen from the groups of formulae (X₁-5) to (X₁-10) below:

d) the compounds corresponding to formula (I-d) below:

in which:

-   -   the unit B is a thiophenyl, phenyl, aminothiazolyl,         benzothiazolyl or 2-pyridyl group,     -   L is a heterocycle chosen from the rings of formulae (L-1) to         (L-25) below:

-   -   q is an integer equal to 0 or 1, and     -   Z₁ represents a carbon or nitrogen atom, it being understood         that when Z₁ is a carbon atom, then q=0;

e) the compounds corresponding to formula (I-e) below:

in which X₂ is chosen from the groups (X₂-1) to (X₂-23) below:

Among the compounds of formula (I-d) hereinabove, those in which the unit B represents a thiophenyl group are particularly preferred.

As compounds of formula (I) in accordance with the invention, mention may be made of:

-   2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (illustrated by formula (I-1) in Example 2 hereinbelow); -   2-azido-1-[4-(3-cyclopropyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 14); -   2-azido-1-[4-(3-pyrid-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 13): -   2-azido-1-{4-[3-(3-chloro-2-methylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone     (compound 6); -   2-azido-1-[4-(3-pyrid-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; -   2-azido-1-{4-[3-(2-fluoro-5-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone; -   2-azido-1-{4-[3-(2,5-difluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 7); -   2-azido-1-{4-[3-(2-methoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 11); -   2-azido-1-{4-[3-(2-chlorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 10); -   2-azido-1-[4-(3-phenyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 4); -   2-azido-1-{4-[3-(3-trifluoromethoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone; -   2-azido-1-{4-[3-(4-tert-butylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 9); -   2-azido-1-{4-[3-(4-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone     (compound 8); -   2-azido-1-[4-(3-benzo[1,3]dioxol-5-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 12); -   2-azido-1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 2); -   2-azido-1-{4-[3-(4-fluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 5); -   2-azido-1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 3); -   2-azido-1-[4-(3-(6-methoxybenzothiazol-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 15); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     (illustrated by formula (I-2) in Example 3 hereinbelow); -   the t-butyl ester of     4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperidine-1-carboxylic acid     (illustrated by formula (I-3) in Example 1 hereinbelow); -   the t-butyl ester of     4-(3-cyclopropyl[1,2,4-]oxadiazol-5-yl)piperidine-1-carboxylic acid; -   the t-butyl ester of     4-(3-pyrid-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid; -   the t-butyl ester of     4-[3-(3-chloro-2-methylphenyl)[1,2,4]oxadiazol-5-yl]-piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-(3-pyrid-3-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid; -   the t-butyl ester of     4-[3-(2-fluoro-5-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(2,5-difluorophenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(2-methoxyphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(2-chlorophenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-(3-phenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid; -   the t-butyl ester of     4-[3-(3-trifluoromethoxyphenyl)[1,2,4]oxadiazol-5-yl]-piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(4-tert-butylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(4-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]-piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-(3-benzo[1,3]dioxol-5-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid; -   the t-butyl ester of     4-[3-(4-fluorophenyl)[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   the t-butyl ester of     4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   the t-butyl ester of     3-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   the t-butyl ester of     2-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)pyrrolidine-1-carboxylic     acid; -   the t-butyl ester of     4-[3-(6-methoxybenzothiazol-2-yl)[1,2,4]oxadiazol-5-yl]-piperidine-1-carboxylic     acid; -   the t-butyl ester of     [2-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)ethyl]carbamic acid; -   the t-butyl ester of     [3-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)propyl]carbamic acid; -   the t-butyl ester of     [4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)butyl]carbamic acid; -   the t-butyl ester of     [5-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)pentyl]carbamic acid; -   4-iodo-N-(1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethyl}-1H-1,2,3-triazol-4-ylmethyl)benzenesulfonamide     (illustrated by formula (I-4) in Example 4 hereinbelow); -   the t-butyl ester of     4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-ylmethyl)piperazine-1-carboxylic     acid (illustrated by formula (I-5) in Example 5 hereinbelow); -   the t-butyl ester of     4-(5-thiophen-2-yl[1,2,4]oxadiazol-3-ylmethyl)piperazine-1-carboxylic     acid (illustrated by formula (I-6) in Example 6 hereinbelow); -   the t-butyl ester of     4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperidine-1-carboxylic     acid (illustrated by formula (I-7) in Example 7 hereinbelow); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone     of formula (I-8) below:

-   2-(2,2,2-trifluoroacetyl)-1,2,3,4-tetrahydroisoquinoline-7-sulfonic     acid     (1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-[1,2,3]triazol-4-ylmethyl)amide     of formula (I-9) below:

-   2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-ylmethyl)piperazin-1-yl]ethanone     of formula (I-10) below:

-   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-ylmethyl)piperazin-1-yl]-2-[1,2,3]triazol-1-ylethanone     of formula (I-11) below:

-   2-azido-1-[4-(5-thiophen-2-yl[1,2,4]oxadiazol-3-ylmethyl)piperazin-1-yl]ethanone     of formula (I-12) below:

-   1-[4-(5-thiophen-2-yl[1,2,4]oxadiazol-3-ylmethyl)piperazin-1-yl]-2-[1,2,3]-triazol-1-ylethanone     of formula (I-13) below:

-   2-azido-1-[4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperid-1-yl]ethanone     of formula (I-14) below:

-   1-[4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone     of formula (I-15) below:

-   2-azido-1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     of formula (I-16) below:

-   1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     of formula (I-17) below:

-   2-azido-1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     of formula (I-18) below:

-   1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone     of formula (I-19) below:

-   the allylic ester of     4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   2-phenoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 45); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 23); -   3-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 34); -   3,3-dimethyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 26); -   2-thiophen-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 43); -   3-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 24); -   4-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentan-1-one     (Compound 25); -   2-bicyclo[2.2.1]hept-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 40); -   2-cyclopropyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 33); -   3-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 38); -   2-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 41); -   3-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 42); -   2-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 37); -   2-cyclopent-2-enyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (Compound 36); -   2-(4-methylcyclohexyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (Compound 39); -   3-tert-butoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (compound 30); -   2-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 35); -   4,4,4-trifluoro-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 27); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-en-1-one     (Compound 20); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-yn-1-one     (Compound 21); -   3-oxo-3-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propionitrile     (Compound 22); -   2-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 28); -   3-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 29); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 17); -   4-oxo-4-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butyric     acid (Compound 31); -   5-oxo-5-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentanoic     acid (Compound 32); -   4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid     phenylamide (Compound 48); -   4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carbothioic     acid phenylamide (Compound 49); -   4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid     thiophen-2-ylamide (Compound 50); -   4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carbothioic     acid cyclopropylamide (Compound 52); -   4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid     cyclopropylamide (Compound 51); -   1-phenylmethanesulfonyl-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine     (Compound 53); -   1-(thiophene-3-sulfonyl)-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine; -   phenyl[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]methanone     (Compound 54); -   2-thiophen-3-yl-1-[4-(3-thiophen-2-yl[1,2,4]triazol-5-yl)piperid-1-yl]ethanone     (Compound 60); -   1-{4-[3-(5-bromothiophen-2-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-2-thiophen-2-ylethanone     (compound 58); -   3-{4-[3-(5-bromothiophen-2-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-3-oxo-propionitrile     (compound 59); -   2-(2-aminothiazol-4-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; -   1-{4-[3-(2-aminothiazol-5-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-2-cyclopropyl-ethanone; -   2-cyclopropyl-1-{4-[3-(3-dibenzylaminophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 57); -   2-(1H-tetrazol-5-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (compound 61); -   2-(2-chlorophenyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (compound 62); -   2-(2,6-dichlorophenyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (compound 63); and -   2-pyrid-4-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 64).

The compounds of formula (I) as defined above are particularly effective for preventing and/or treating tuberculosis, leprosy or atypical mycobacterioses.

Consequently, according to one advantageous embodiment of the invention, said medicament is intended for preventing and/or treating tuberculosis, leprosy or atypical mycobacterioses.

The compounds of formula (I) used in accordance with the invention have the property of potentiating the activity of the antibiotic ethionamide with respect to mycobacterial strains, while at the same time being much easier to formulate than hexadecyl octanoate.

Consequently, according to one preferred embodiment of the invention, said compounds of formula (I) are used for the preparation of a medicament also comprising at least one antibiotic chosen from antibiotics that are activatable via the EthA enzymatic pathway.

In this case, said antibiotic is preferably chosen from ethionamide, prothionamide, isoxyl and thiacetazone.

The compounds of formula (I) as defined above may be incorporated into a pharmaceutical composition for preventing and/or treating mycobacterial infections.

The invention thus also relates to a pharmaceutical composition comprising, as active principle, at least one compound of formula (I) as defined above, at least one pharmaceutically acceptable excipient and at least one antibiotic that is activatable via the EthA enzymatic pathway.

In this case, the antibiotic is preferably chosen from ethionamide, prothionamide, isoxyl and thiacetazone.

In the pharmaceutical compositions in accordance with the invention, the compound(s) of formula (I) is (are) preferably used in an amount allowing the administration of unit doses of between 1 mg and 1 g approximately.

In the pharmaceutical compositions in accordance with the invention, the antibiotic(s) that is (are) activatable via the EthA enzymatic pathway is (are) used in an amount allowing the administration of unit doses less than or equal to the doses usually recommended by the WHO (WHO, Treatment of tuberculosis: Guidelines for National Programmes. 2003; WHO/CDS/TB2003.313.), national or nongovernmental health organizations, or competent pharmaceutical laboratories.

The compounds of formula (I) used in accordance with the invention have the advantage of allowing a reduction of the effective dose of the antibiotic used by a factor ranging from 2 to 100. In the case of the combination with ETH, the compounds of formula (I) used in accordance with the invention make it possible in particular to reduce the effective dose by a factor ranging from 2 to 50.

When the compound of formula (I) is the compound of formula (I-3), this factor is about 10-fold; when it is the compound of formula (I-1), this factor is between 10 and 20-fold approximately; when it is compound 33, this factor is about 20-fold; when it is compound 43, this factor is about 40-fold; when it is compound 20, this factor is about 20-fold, and when it is compound 22, this factor is about 10-fold.

A person skilled in the art will select one or more pharmaceutically acceptable excipients as a function of the route of administration of the pharmaceutical composition.

Needless to say, a person skilled in the art will take care at that time to ensure that the excipient(s) used is (are) compatible with the intrinsic properties associated with the composition in accordance with the present invention.

In addition, the form of the medicament or of the pharmaceutical composition (for example a solution, a suspension, an emulsion, tablets, gel capsules, suppositories, etc.) will depend on the chosen route of administration.

Thus, for the purposes of the present invention, the medicament or the pharmaceutical composition may be administered via any suitable route, for example via the oral, anal, local, systemic, intravenous, intramuscular or mucosal route, or alternatively using a patch, or else in encapsulated form in, or immobilized on, liposomes, microparticles, microcapsules, and the like.

Nonlimiting examples of excipients that are suitable for oral administration especially include talc, lactose, starch and its derivatives, cellulose and its derivatives, polyethylene glycols, acrylic acid polymers, gelatin, magnesium stearate, animal, plant or synthetic fats, paraffin derivatives, glycols, stabilizers, preserving agents, antioxidants, wetting agents, anticaking agents, dispersants, emulsifiers, flavor enhancers, penetrants, solubilizers, etc.

The techniques for formulating and administering medicaments and pharmaceutical compositions are well known in the art under consideration herein, and a person skilled in the art may especially refer to the latest edition of “Remington's Pharmaceutical Sciences”.

In addition, the invention also relates to products containing at least one compound of formula (I) as defined previously and at least one antibiotic chosen from antibiotics that are activatable via the EthA enzymatic pathway, in particular from ETH, prothionamide, isoxyl and thiacetazone, as combination products for simultaneous, separate or sequential use over time in general anti-tuberculous, anti-lepromatous or anti-mycobacterial therapy.

Certain compounds of formula (I) as described hereinabove are novel per se and, in this respect, constitute another subject of the invention.

These compounds correspond to formula (I′) below: A′-L′-B′  (I′)

in which:

-   -   the unit A′ is connected to L′ via at least one covalent bond         and is chosen from the groups of formula (II′) below:

in which:

-   -   the arrow indicates the point of attachment of the covalent bond         connecting X′₁ to L′, said bond involving at least one carbon         atom of the group X′₁ and a carbon, nitrogen or oxygen atom of         the group L′,     -   n′ is an integer equal to 0 or 1,     -   when n′=1, X′₁ represents a group chosen from C₂-C₅ alkyl         chains; it being understood that a carbon atom of the group X′₁         is engaged in the covalent bond connecting X′₁ to —NH—,     -   when n′=0, X′₁ represents piperidine, piperazine or         tetrahydropyridine, it being understood that the covalent bond         connecting X′₁ to X′₂ involves a ring nitrogen atom of the group         X′₁ and when X′₁ represents piperidine or piperazine, then the         bond between X′₁ and L′ is a 1→4 bond;     -   X′₂ is chosen from the groups of formulae (III′a) and (III′b)         below:

in which:

-   -   the arrow indicates the point of attachment of the covalent bond         between X′₂ and —NH— when n′=1 or between X′₂ and X′₁ when n′=0,     -   X′₃ is O or S,     -   Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which:         -   p′ and m′, independently of each other, are integers equal             to 0 or 1;         -   T′ is chosen from O, NH and CH₂; and         -   R′₁ is chosen from a hydrogen atom; a linear or branched             C₂-C₄ alkyl radical; a linear or branched C₂-C₄ haloalkyl             radical; a C₂-C₄ alkene radical; a C₂-C₄ alkyne radical; a             linear C₂-C₄ alkoxy radical; a (C₂-C₄)alkylcarboxylic group;             a cyano group; a saturated or unsaturated C₃-C₆             hydrocarbon-based ring optionally substituted with a C₁-C₄             alkyl radical or with a methylene bridge; an azido group; a             benzyloxy group; an aromatic or heteroaromatic ring             optionally substituted with one or more substituents chosen             from a halogen atom and an amino, linear or branched C₁-C₄             alkyl, C₁-C₄ alkoxy or cyano group; or a triazole ring which             is unsubstituted or substituted, in position 4, with a             trimethylsilyl group or a group chosen from the compounds of             formula (IV′) below:

in which:

-   -   the arrow represents the point of attachment of the compound of         formula (IV′) to X′₂ via a covalent bond,     -   R′₂ and R′₃, which may be identical or different, represent a         hydrogen atom, a halogen atom preferably chosen from chlorine,         iodine and fluorine, a C₁-C₄ alkyl group or a nitro group; when         R′₂ and R′₃ are adjacent, they may also form a methylenedioxy         group or, together with the carbon atoms of the benzene ring on         which they are borne, a 6-membered carbon-based or         heterocarbon-based ring, said ring being optionally substituted         with a di(C₁-C₄)alkylamino radical or a trifluoroacetyl radical;     -   the unit B′ is connected to L′ via at least one covalent bond         and is chosen from aromatic hydrocarbon-based rings,         polyaromatic hydrocarbon-based rings, C₅ heteroaromatic rings         containing at least one heteroatom chosen from S, O and N,         pyrid-2-yl, saturated or unsaturated C₃-C₇ hydrocarbon-based         rings, saturated or unsaturated C₃-C₇ heterocycles, and a         benzothiazolyl group; said rings or said group possibly being         unsubstituted or substituted with one or more substituents         chosen from halogen atoms, linear or branched C₁-C₄ alkyl         radicals, linear or branched C₁-C₄ alkoxy radicals, a         methylenedioxy group, linear or branched C₁-C₄ haloalkyl         radicals, linear or branched C₁-C₄ haloalkoxy radicals and an         amino group which is unsubstituted or substituted with one or         two benzyl groups;     -   L′ represents a group that provides the bond between the two         units A′ and B′ and is chosen from unsaturated 5-membered         heterocycles comprising from 1 to 4 heteroatoms chosen from N, O         and S;

it being understood that when R′₁ represents a linear or branched C₂-C₄ alkoxy group and when p′=1, then T′ is chosen from NH and CH₂.

When n′=1 and when X₁′ represents a C₂-C₅ alkyl chain, this chain is preferably chosen from ethane, propane, butane and pentane chains.

When X₂′ represents a group of formula (III′a), this group is then preferably a group in which X₃′ represents O, Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=0, m′=1 and R′₁ represents an azido or thiophenyl group that is unsubstituted or substituted with one or more halogen atoms.

Among the groups of formula (II′) hereinabove, mention may be made of those in which:

-   -   n′=1, X′₁ represents a C₂-C₅ alkyl chain and X′₂ represents a         group of formula (III′a) in which, X′₃ represents O or S, Y′ is         a group -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=1 and T represents         an oxygen atom, m′=1 and R′₁ represents a linear or branched         C₂-C₄ alkyl radical;     -   n′=0, X′₁ represents piperidine or piperazine that is         1,4-substituted and X′₂ represents a group of formula (III′a) in         which X′₃ represents O or S, Y′ is a group         -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=0, m′=1 and R′₁ represents         an azido group, a cyano group or a heteroaromatic ring,         preferably thiophene or triazole;     -   n′=0, X′₁ represents piperidine or piperazine that is         1,4-substituted and X′₂ represents a group of formula (III′a) in         which X′₃ represents O or S, Y′ is a group         -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=1 and T′=CH₂, m′=1 and R′₁         represents a saturated C₃-C₇ hydrocarbon-based ring;     -   n′=0, X′₁ represents piperidine or piperazine that is         1,4-substituted and X′₂ represents a group of formula (III′a) in         which X′₃ represents O or S, Y′ is a group         -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=0, m′=0 and R′₁ represents         a benzyloxy group;     -   n′=0, X′₁ represents piperidine or piperazine that is         1,4-substituted, and X′₂ represents a group of formula (III′a)         in which X′₃ represents O or S, Y′ is a group         -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=0 or 1, m′=1 and R′₁         represents a triazole ring substituted with a compound of         formula (IV′) in which:

i) R′₂ and R′₃ represent a hydrogen atom,

ii) R′₂ represents a hydrogen atom and R′₃ represents a halogen atom or a methyl radical, preferably in the para position relative to the sulfonamide function,

iii) R′₂ represents a nitro group in the ortho or meta position relative to the sulfonamide function and R′₃, in the para position relative to the sulfonamide function, represents a hydrogen or halogen atom;

iv) R′₂ and R′₃, in the ortho and meta positions, form a benzene ring optionally substituted with a dimethylamino group;

v) R′₂ and R′₃, in the meta and para positions, form a piperidino ring in which the nitrogen atom is substituted with a trifluoroacetyl radical.

When the unit B′ is an aromatic hydrocarbon-based ring, said ring is preferably chosen from phenyl and phenyl substituted with one or more halogen atoms and/or one or more groups chosen from methyl, t-butyl, trifluoromethyl, trifluoromethyloxy, methyloxy, dibenzylamino and methylenedioxy groups.

When the unit B′ is a heterocycle, said ring is preferably chosen from thiophene, furan, 2-pyridine, aminothiazole and benzothiazole rings.

When the unit B′ is a saturated hydrocarbon-based ring, it preferably represents a cyclopropane.

According to the invention, the unit B′ is preferably chosen from phenyl, thiophenyl, furyl, 2-amino-(1-3)thiazol-5-yl, pyrid-2-yl, 4′-t-butylphenyl, 4′-trifluoromethylphenyl, 2′,3′-methylenedioxyphenyl, 4′-fluorophenyl, 2′-methyl-3′-chlorophenyl, 2′-trifluoromethyl-5′-fluorophenyl, 2′-trifluoromethyloxyphenyl, 2′,5′-difluorophenyl, 2′-chlorophenyl, 2′-methyloxyphenyl, cyclopropanyl and benzothiazolyl groups.

According to one particularly preferred embodiment of the invention, the unit B′ is chosen from thiophenyl, phenyl, fluorophenyl, aminothiazolyl, benzothiazolyl and pyrid-2-yl groups.

According to the invention, when L′ represents an unsaturated 5-membered heterocycle, it is preferably chosen from oxadiazole, triazole, isoxazole, imidazole, thiadiazole, pyrrole, tetrazole, furan, thiophene, pyrazole and thiazole rings.

As compounds of formula (I′) that are used in accordance with the invention, mention may be made in particular of:

a) the compounds corresponding to formula (I′-a) below:

in which the unit B′ is chosen from the groups of formulae (B′-1) to (B′-11) and (B′-14) to (B′-21) below:

b) the compounds corresponding to formula (I′-b) below:

in which X′₁ is chosen from the groups of formulae (X₁′-1) to (X₁′-4) below:

c) the compounds corresponding to formula (I′-c) below:

in which X′₁ is chosen from the groups of formulae (X₁′-8) to (X₁′-10) below:

d) the compounds corresponding to formula (I′-d) below:

in which:

-   -   the unit B′ is a thiophenyl, phenyl, aminothiazolyl,         benzothiazolyl or 2-pyridyl group,     -   L′ is a heterocycle chosen from the rings of formulae (L′-1) to         (L′-25) below:

-   -   q′ is an integer equal to 0 or 1, and     -   Z′₁ represents a carbon or nitrogen atom, it being understood         that when Z′₁ is a carbon atom, then q′=0;

e) the compounds corresponding to formula (I′-e) below:

in which X₂′ is chosen from the groups (X₂′-1) to (X₂′-23) below:

Among the compounds of formula (I′-d) hereinabove, those in which the unit B′ represents a thiophenyl group are particularly preferred.

As compounds of formula (I′) in accordance with the invention, mention may be made of:

-   2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (illustrated by formula (I-1) in Example 2 hereinbelow); -   2-azido-1-[4-(3-cyclopropyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 14); -   2-azido-1-[4-(3-pyrid-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 13): -   2-azido-1-{4-[3-(3-chloro-2-methylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone     (compound 6); -   2-azido-1-{4-[3-(2-fluoro-5-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone; -   2-azido-1-{4-[3-(2,5-difluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 7); -   2-azido-1-{4-[3-(2-methoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 11); -   2-azido-1-{4-[3-(2-chlorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 10); -   2-azido-1-[4-(3-phenyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 4); -   2-azido-1-{4-[3-(3-trifluoromethoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone; -   2-azido-1-{4-[3-(4-tert-butyl     phenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (compound 9); -   2-azido-1-{4-[3-(4-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone     (compound 8); -   2-azido-1-[4-(3-benzo[1,3]dioxol-5-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 12); -   2-azido-1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 2); -   2-azido-1-{4-[3-(4-fluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone     (compound 5); -   2-azido-1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 3); -   2-azido-1-[4-(3-(6-methoxybenzothiazol-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 15); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     (illustrated by formula (I-2) in Example 3 hereinbelow); -   4-iodo-N-(1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethyl}-1H-1,2,3-triazol-4-ylmethyl)benzenesulfonamide     (illustrated by formula (I-4) in Example 4 hereinbelow); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     of formula (I-8) below:

-   2-(2,2,2-trifluoroacetyl)-1,2,3,4-tetrahydroisoquinoline-7-sulfonic     acid     (1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-[1,2,3]-triazol-4-ylmethyl)amide     of formula (I-9) below:

-   2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl-methyl)piperazin-1-yl]-ethanone     of formula (I-10) below:

-   2-azido-1-[4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperid-1-yl]ethanone     of formula (I-14) below:

-   1-[4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     of formula (I-15) below:

-   2-azido-1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     of formula (I-16) below:

-   1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-yl-ethanone     of formula (I-17) below:

-   2-azido-1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     of to formula (I-18) below:

-   1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone     of formula (I-19) below:

-   the allylic ester of     4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic     acid; -   2-phenoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 45); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 23); -   3-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 34); -   3,3-dimethyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 26); -   2-thiophen-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 43); -   3-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 24); -   4-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentan-1-one     (Compound 25); -   2-bicyclo[2.2.1]hept-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (Compound 40); -   2-cyclopropyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 33); -   3-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 38); -   2-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (compound 41); -   3-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 42); -   2-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 37); -   2-cyclopent-2-enyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (Compound 36); -   2-(4-methylcyclohexyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone     (Compound 39); -   3-tert-butoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (compound 30); -   2-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 35); -   4,4,4-trifluoro-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one     (Compound 27); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-en-1-one     (Compound 20); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-yn-1-one     (Compound 21); -   3-oxo-3-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propionitrile     (Compound 22); -   2-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 28); -   3-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one     (Compound 29); -   1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone     (Compound 17); -   4-oxo-4-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butyric     acid (Compound 31); -   5-oxo-5-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentanoic     acid (Compound 32); -   1-phenylmethanesulfonyl-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine     (Compound 53); -   1-(thiophene-3-sulfonyl)-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine; -   phenyl[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]methanone     (Compound 54); -   1-{4-[3-(5-bromothiophen-2-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-2-thiophen-2-ylethanone     (compound 58); -   3-{4-[3-(5-bromothiophen-2-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-3-oxo-propionitrile     (compound 59); -   2-thiophen-3-yl-1-[4-(3-thiophen-2-yl[1,2,4]triazol-5-yl)piperid-1-yl]ethanone     (Compound 60); -   2-(2-aminothiazol-4-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; -   1-{4-[3-(2-aminothiazol-5-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-2-cyclopropyl-ethanone; -   2-cyclopropyl-1-{4-[3-(3-dibenzylaminophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone; -   2-(1H-tetrazol-5-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone; -   2-(2-chlorophenyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone; -   2-(2,6-dichlorophenyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone;     and -   2-pyrid-4-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone.

The compounds of formula (I′) in accordance with the invention may be readily prepared, generally in two, three or four steps, according to synthetic processes similar to the standard processes that are well known to those skilled in the art.

Thus, the compounds of formula (I′) in which the unit A′ represents a group of formula (II′) in which n′=0, X₁′ represents piperidine and X₂′ represents a group of formula (III′a) in which X₃′ represents an oxygen atom, Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which, p′=0, m′=1 and R′₁ represents an azido group and in which the group L′ represents an oxadiazole ring and the unit B′ is as defined previously, may be prepared, for example, according to the process represented in reaction scheme A hereinbelow:

according to which, in a first step, the mono-tert-butylpiperidine-1,4-carboxylic acid ester is reacted, in solution in an organic solvent, with a compound of formula (V′) in which B′ has the same meaning as that given previously, in the presence of O-benzotriazole-1-yl-N,N,N′,N′-tetramethyluronium tetrafluoro-borate and hydroxybenzotriazole hydrate, to give a compound of formula (VI′), which, in a second step, is deprotected in the presence of hydrochloric acid to give the compounds of formula (VII′), which, in a third step, is reacted, in an organic solvent in the presence of chloroacetyl chloride and triethylamine, and is finally subjected, in a fourth step, to a nucleophilic substitution in the presence of sodium azide, to give the expected compound of formula (I′) (Poulain R. F. et al., Tetrahedron Letters, 2001, 42, 1495-1498 and Evans M. D. et al., Tetrahedron Letters, 2003, 44, 9337-9341).

According to the process shown in Scheme A, the first step is preferably performed at a temperature of between 100 and 120° C. and the organic solvent is preferably dimethylformamide. The time required perform the first step is generally between 6 and 18 hours. The second step is preferably performed at room temperature using ethanol as reaction solvent. The time required to perform the second step is generally between 3 and 6 hours.

The compounds of formula (I′) in which the unit A′ represents a group of formula (II′) in which n′=1, X′₁ represents one of the groups of formulae (X₁′-1) to (X₁′-4) and X₂′ represents a group of formula (III′a) in which X₃′ is an oxygen atom, Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R′₁ in which p′=0, m′=1 and R′₁ represents an azido group and in which the group L′ represents an oxadiazole ring and the unit B′ is as defined previously, may be prepared, for example, according to the process shown in reaction scheme B hereinbelow:

according to which steps 1 to 4 are performed as described previously for steps 1 to 4 of the process shown in scheme A hereinabove, using as starting material a compound of formula (IX′) above in which X₁′ is chosen from the groups (X₁′-1) to (X₁′-4) as described previously.

The compounds of formula (I′) in which the unit A′ represents a group of formula (II′) for which n′=0, X₁′ represents piperidine and X₂′ represents a group of formula (III′a) in which X₃′ represents an oxygen atom, Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R₁′ in which p′=0, m′=1 and R₁′ represents a triazole group substituted with a trimethylsilyl group or a group chosen from the compounds of formula (IV′) described above and in which the group L′ represents an oxadiazole ring and the unit B′ is as defined previously, may be prepared, for example, according to the process shown in reaction scheme C hereinbelow:

according to which the compounds of formula (I′-a), in which B′ has the same meaning as that indicated previously, are reacted, in solution in acetonitrile, in the presence of a compound of formula (XIII′) in which R₁′ has the same meaning as that indicated previously, in the presence of copper iodide, to obtain the expected compound of formula (I′) (Krasinski, A. et al., J. Am. Chem. Soc., 2005; 127(18), 6686-6692).

The compounds of formula (I′) in which the unit A′ represents a group of formula (II′) for which n′=0, X₁′ represents piperidine and X₂′ represents a group of formula (III′a) in which X₃′ represents an oxygen atom, Y′ represents a group -(T′)_(p′)-(CH₂)_(m′)—R₁′ in which p′=0, m′=1 and R₁′ represents a triazole group and in which the group L′ represents an oxadiazole ring and the unit B′ is as defined previously, may be prepared, for example, according to the process shown in reaction scheme D hereinbelow:

according to which the particular compounds of formula (I′) above, in which B′ has the same meaning as that indicated previously, are reacted, in solution in tetrahydrofuran, in the presence of tetrabutylammonium fluoride, to obtain the expected compound of formula (I′).

When the synthesis is complete, the compounds of formula (I′) may, if necessary, be purified according to the methods that are well known to those skilled in the art.

Another subject of the present invention is also a pharmaceutical composition comprising, as active principle, at least one compound of formula (I′) as defined previously and at least one pharmaceutically acceptable excipient.

BRIEF DESCRIPTION OF THE DRAWINGS

Besides the preceding provisions, the invention also comprises other provisions that will emerge from the description that follows, which refers to examples of synthesis of compounds of formula (I), to an example of demonstration of the potentiating effect on ETH activity by a compound of formula (I), and also to the attached figures, in which

FIG. 1 is a photograph of three Petri dishes after inoculating and culturing M tuberculosis mycobacteria on agar gel as a function of the presence or absence of a dose of ETH (2 or 4 μg) optionally combined with 20 nmol of compound of formula (I-3); and.

FIG. 2 is a graph showing the ethionamide-potentiating effect of compound (I-1) evaluated according to the RIA detection method in liquid medium on the Bactec® 460 robot in 12 B medium, in which the growth index (arbitrary units) is presented as a function of the time in days.

EXAMPLES

It should be clearly understood that these examples are given purely as illustrations of the subject of the invention, of which they do not in any way constitute a limitation.

Example 1 Synthesis of the t-butyl ester of 4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperidine-1-carboxylic acid (Compound of formula (I-3))

1) First Step: Synthesis of N-hydroxythiophene-2-carboxamidine

A solution of sodium ethoxide (21% by weight in ethanol, 64.9 ml, 0.174 mol, 1.1 eq.), hydroxylamine hydrochloride (12.1 g, 0.174 mol, 1.1 eq.) and ethanol (100 ml) was refluxed for 30 minutes. Thiophene-2-carbonitrile (18.8 g; 0.172 mol; 1 eq.) was then added and the solution was refluxed continuously for 18 hours. The reaction was monitored by thin layer chromatography (TLC) (50/50 cyclohexane/pentane). The solution was evaporated under reduced pressure and the residue obtained triturated in water at pH 7. The aqueous phase, saturated beforehand with NaCl, was then extracted with ethyl ether (three times). The organic phases were combined, dried over MgSO₄ and concentrated under reduced pressure to give a white powder.

Proton NMR (DMSO-d6, δ): 9.60 (s, 1H), 7.36 (dd, J=4.8 Hz, J=0.9 Hz, 1H), 7.40 (dd, J=3.6 Hz, J=0.9 Hz, 1H), 7.03 (dd, J=4.8 Hz, J=3.6 Hz, 1H), 5.93 (brs, 2H).

MS m/z: 143 (M⁺+1).

2) Second Step: Synthesis of the t-butyl ester of 4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperidine-1-carboxylic acid of formula (I-3)

2.293 g (1 eq.) of the mono-tert-butyl ester of piperidine-1,4-dicarboxylic acid, 3.210 g (1 eq.) of O-benzotriazol-1-yl-N,N,N′N′-tetramethyluronium tetrafluoroborate (TBTU), 306.2 mg (0.2 eq.) of 1-hydroxybenzotriazole hydrate (HOBT) and 8.56 ml (5 eq.) of ethyldiisopropyl-amine were added to 50 ml of dimethylformamide (DMF) in a sealed tube, and stirred for 1 minute. 1.422 g (1 eq.) of N-hydroxythiophene-2-carboxamidine were then added to the suspension. The resulting mixture was stirred at room temperature for 1 hour and then at 110° C. for 6 hours. The DMF was then evaporated off, and the residue was purified on silica gel (90/10 cyclohexane/ethyl acetate). The compound of formula (I-3) was obtained in the form of a white solid, in a yield of 40%.

Proton NMR (DMSO-d6, δ): 7.85 (dd, J=5.0 Hz, J=1.1 Hz, 1H), 7.77 (dd, J=3.8 Hz, J=1.1 Hz), 7.25 (dd, J=5.0 Hz, J=3.8 Hz, 1H), 3.90 (d, J=13.3 Hz, 2H), 3.26 (m, 1H), 2.10 (dd, J=13.3 Hz, J=3.0 Hz, 2H), 1.65 (m, 2H), 1.35 (s, 9H)

MS m/z: 358 (M⁺+Na)

The following compounds were synthesized according to the same protocol as that described above for the compound of formula (I-3):

t-Butyl ester of 4-(3-cyclopropyl[1,2,4-]oxadiazol-5-yl)piperidine-1-carboxylic acid

MS m/z: 294 (M⁺+1) and 238 (M⁺-55)

t-Butyl ester of 4-(3-pyrid-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

MS m/z: 331 (M⁺+1)

¹H NMR (CDCl₃): δ 8.82 (dd, J=4.9 Hz J=1.2 Hz, 1H), 8.14 (dd, J=7.8 Hz J=1.8 Hz, 1H), 7.88 (td, J=7.8 Hz J=7.8 Hz J=1.8 Hz, 1H), 7.46 (ddd, J=7.8 Hz J=4.9 Hz J=1.2 Hz, 1H), 4.14 (m, 2H), 3.21 (m, 1H), 2.98 (m, 2H), 2.15 (m, 2H), 1.93 (m, 2H), 1.47 (s, 9H).

t-Butyl ester of 4-[3-(3-chloro-2-methylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 378 (M⁺+1) and 322 (M⁺−55)

¹H NMR (CDCl₃): δ 7.77 (dd, J=7.9 Hz J=1.1 Hz, 1H), 7.50 (dd, J=7.5 Hz J=1.1 Hz, 1H), 7.22 (t, J=7.9 Hz, 1H), 4.12 (m, 2H), 3.18 (m, 1H), 3.00 (m, 2H), 2.63 (s, 3H), 2.13 (m, 2H), 1.88 (m, 2H), 1.47 (s, 9H)

¹³C NMR (CDCl₃): δ 184.89, 180.66, 168.55, 154.64, 136.09, 131.51, 128.81, 128.27, 126.76, 79.92, 34.41, 29.15, 28.43, 18.10.

t-Butyl ester of 4-(3-pyrid-3-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

MS m/z: 331 (M⁺+1) and 231 (M⁺−99)

t-Butyl ester of 4-[3-(2-fluoro-5-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 416 (M⁺+1) and 360 (M⁺−55)

¹H NMR (CDCl₃): δ 8.37 (dd, J=6.3 Hz J=2.3 Hz, 1H), 7.78 (m, 1H), 7.37 (t, J=9.2 Hz, 1H), 4.14 (m, 2H), 3.21 (m, 1H), 3.00 (m, 2H), 2.17 (m, 2H), 1.91 (m, 2H), 1.48 (s, 9H).

¹³C NMR (CDCl₃): δ 182.47, 165.08, 162.32, 161.58, 155.61, 130.86, 129.50, 118.72, 80.94, 35.48, 30.14, 29.43.

t-Butyl ester of 4-[3-(2,5-difluorophenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 366 (M⁺+1) and 310 (M⁺−55)

¹H NMR (CDCl₃): δ 7.69 (m, 1H), 7.13 (m, 2H), 4.07 (m, 2H), 3.12 (m, 1H), 2.92 (m, 2H), 2.06 (m, 2H), 1.88 (m, 2H), 1.41 (s, 9H).

t-Butyl ester of 4-[3-(2-methoxyphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 360 (M⁺+1) and 304 (M⁺−55)

¹H NMR (DMSO): δ7.80 (dd, J=7.5 Hz J=1.8 Hz, 1H), 7.53 (td, J=7.5 Hz J=7.5 Hz J=1.8 Hz, 1H), 7.20 (dd, J=7.5 Hz J=1.0 Hz, 1H), 7.08 (td, J=7.5 Hz J=7.5 Hz J=1.0 Hz, 1H), 3.92 (m, 2H), 3.84 (s, 3H), 2.95 (m, 2H), 2.04 (m, 2H), 1.62 (m, 2H), 1.39 (s, 9H).

t-Butyl ester of 4-[3-(2-chlorophenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 364 (M⁺+1) and 308 (M⁺−55)

t-Butyl ester of 4-(3-phenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 330 (M⁺+1) and (M⁺−55)

¹H NMR (CDCl₃): δ 8.07 (m, 2H), 7.48 (m, 3H), 6.82 (d, J=8.3 Hz, 1H), 4.13 (m, 2H), 3.16 (m, 1H), 3.00 (m, 2H), 2.12 (m, 2H), 1.90 (m, 2H), 1.48 (s, 9H).

¹³C NMR (CDCl₃): δ 182.29, 169.24, 155.61, 132.15, 129.83, 128.40, 125.00, 80.82, 39.17, 30.17, 29.41.

t-Butyl ester of 4-[3-(3-trifluoromethoxyphenyl)[1,2,4]oxadiazol-5-yl]-piperidine-1-carboxylic acid

MS m/z: 414 (M⁺+1) and 358 (M⁺−55)

¹H NMR (CDCl₃): δ 7.95 (d, J=8.0 Hz, 1H), 7.87 (s, 1H), 7.45 (t, J=8.0 Hz, 1H), 7.28 (d, J=8.0 Hz, 1H), 4.06 (m, 2H), 3.10 (m, 1H), 2.92 (m, 2H), 2.05 (m, 2H), 1.82 (m, 2H), 0.92 (s, 9H).

t-Butyl ester of 4-[3-(4-tert-butylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 386 (M⁺+1) and 330 (M⁺−55)

¹H NMR (CDCl₃): δ 7.95 (d, J=8.0 Hz, 1H), 7.87 (s, 1H), 7.45 (t, J=8.0 Hz, 1H), 7.28 (d, J=8.0 Hz, 1H), 4.06 (m, 2H), 3.10 (m, 1H), 2.92 (m, 2H), 2.05 (m, 2H), 1.82 (m, 2H), 0.92 (s, 9H).

t-Butyl ester of 4-[3-(4-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS m/z: 398 (M⁺+1) and 342 (M⁺−55)

¹H NMR (CDCl₃): δ 8.21 (d, J=8.0 Hz, 2H), 7.74 (d, J=8.0 Hz, 2H), 4.14 (m, 2H), 3.18 (m, 1H), 3.01 (m, 2H), 2.13 (m, 2H), 1.90 (m, 2H), 1.47 (s, 9H).

¹³C NMR (CDCl₃): δ 182.87, 168.30, 155.63, 131.24, 128.80, 126.89, 80.93, 35.55, 30.14, 29.44.

t-Butyl ester of 4-(3-benzo[1,3]-dioxol-5-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

MS m/z: 374 (M⁺+1) and 318 (M⁺−55)

¹H NMR (CDCl₃): δ 7.56 (dd, J=8.3 Hz J=1.5 Hz, 1H), 7.44 (d, J=1.5 Hz, 1H), 6.82 (d, J=8.3 Hz, 1H), 5.97 (s, 2H), 4.05 (m, 2H), 3.07 (m, 1H), 2.91 (m, 2H), 2.05 (m, 2H), 1.83 (m, 2H), 1.40 (s, 9H).

¹³C NMR (CDCl₃): δ 182.07, 155.63, 151.10, 124.91, 123.33, 121.66, 109.70, 109.64, 108.45, 102.59, 80.77, 35.48, 30.13, 29.43.

t-Butyl ester of 4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

¹H NMR: δ=7.62 (dd, J=1.68 Hz, J=0.72 Hz, 1H), 7.14 (dd, J=3.48 Hz, J=0.72 Hz, 1H), 6.57 (dd, J=3.48 Hz, J=1.77 Hz, 1H), 4.14 (m, 2H), 3.15 (m, 1H), 2.94 (m, 2H), 2.11 (m, 2H), 1.86 (m, 2H), 1.49 (s, 9H).

MS m/z: 320 (M⁺+1)

t-Butyl ester of 4-[3-(4-fluorophenyl)[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

MS m/z: 348 (M⁺+1)

¹H NMR (CDCl₃): δ 7.99 (dd, J=8.8 Hz J=3.6 Hz 2H), 7.10 (t, J=8.8 Hz 2H), 4.06 (m, 2H), 3.10 (m, 1H), 2.93 (m, 2H), 2.06 (m, 2H), 1.87 (m, 2H), 1.42 (s, 9H).

t-Butyl ester of 4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

¹H NMR: (CDCl₃): δ=7.6 (dd, J=1.8 Hz, J=0.9 Hz, 1H), 7.11 (dd, J=3.6 Hz, J=0.9 Hz, 1H), 6.56 (dd, J=3.6 Hz, J=1.8 Hz, 1H), 3.15 (m, 1H), 2.95 (m, 2H), 2.1 (m, 2H), 1.9 (m, 4H), 1.47 (s, 9H)

MS m/z: 336 (M⁺+1)

t-Butyl ester of 3-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid

Proton NMR (CDCl₃, δ): 7.80 (dd, J=3.6 Hz, J=2.7 Hz, 1H), 7.51 (m, 1H), 7.20 (t, J=3.6 Hz, 1H), 3.98 (d, J=13.2 Hz, 1H); 3.02 (m, 1H), 2.26 (d, J=4.8 Hz, 1H), 1.48 (s, 9H)

MS m/z: 336 (M⁺+1)

t-Butyl ester of 2-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)pyrrolidine-1-carboxylic acid

Proton NMR (CDCl₃, δ): 7.80 (m, 1H), 7.51 (m, 1H), 7.20 (m, 1H), 3.63 (m, 1H), 3.44 (m, 1H), 2.33 (m, 2.26 (m, 1H), 1.48 (s, 9H)

MS m/z: 322 (M⁺+1)

t-Butyl ester of [2-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)ethyl]carbamic acid

Proton NMR (CDCl₃, δ): 7.72 (dd, J=3.6 Hz, J=2.7 Hz, 1H), 7.44 (dd, J=3.6 Hz, J=2.7 Hz, 1H); 7.09 (t, J=3.9 Hz, 1H); 4.99 (brs, 1H, NH); 3.59 (t, J=6 Hz, 2H); 3.06 (t, J=6 Hz, 2H); 1.37 (s, 9H)

MS m/z: 196 (M⁺−99)

t-Butyl ester of [3-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)propyl]carbamic acid

Proton NMR (CDCl₃, δ): 7.70 (dd, J=3.6 Hz, J=2.7 Hz, 1H), 7.43 (dd, J=5.1 Hz, J=1.2 Hz, 1H), 7.08 (t, J=5.1 Hz, 1H), 4.67 (brs, 1H), 3.21 (t, J=6.6 Hz, 2H), 2.92 (t, J=7.2 Hz, 2H), 2.00 (m, 2H), 1.37 (s, 9H)

MS m/z: 210 (M⁺−99)

t-Butyl ester of [4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)butyl]carbamic acid

Proton NMR (DMSO-d6, δ): 7.70 (m, 1H); 7.43 (m, 1H); 7.08 (m, 1H); 4.53 (brs, 1H, NH); 3.11 (m, 2H); 2.09 (m, 2H); 1.79 (m, 2H); 1.56 (m, 2H); 1.35 (s, 9H).

MS m/z: 224 (M⁺−99)

t-Butyl ester of [5-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)pentyl]carbamic acid

Proton NMR (DMSO-d6, δ): 7.42 (m, 1H); 7.08 (m, 1H); 4.48 (brs, 1H, NH); 3.06 (m, 2H); 2.89 (m, 2H); 1.82 (m, 2H); 1.48 (m, 4H); 1.36 (s, 9H).

MS m/z: 238 (M⁺-99)

t-Butyl ester of 4-[3-(6-methoxybenzothiazol-2-yl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

MS: m/z 417 (M+H⁺)

¹H NMR (CDCl₃): δ 8.11 (d, J=8.8 Hz, 1H), 7.37 (s, 1H), δ 7.15 (d, J=8.8 Hz, 1H), 4.15 (m, 2H), 3.90 (s, 3H), 3.23 (m, 1H), 2.97 (m, 2H), 2.14 (m, 2H), 1.96 (m, 2H), 1.47 (s, 9H).

¹³C NMR (CDCl₃): δ 182.62, 164.49, 159.17, 154.59, 148.07, 145.28, 137.14, 125.36, 117.03, 103.64, 79.94, 55.86, 42.96, 34.72, 29.08, 28.43.

Example 2 Synthesis of 2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (compound (I-1))

1) First Step: Synthesis of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidinium hydrochloride

11 g of the tert-butyl ester of 4-(3-thiophen-2-yl[1,2,4]-oxadiazol-5-yl)piperidine-1-carboxylic acid (32.8 mmol) were placed in a 250 ml round-bottomed flask and dissolved in 66 ml of absolute ethanol. A solution of hydrogen chloride in dioxane (4N) (10 ml) was then added. The reaction medium was heated at 50° C. for 2 hours. The solution was then cooled and 100 ml of diethyl ether were added. The product was then filtered off. 9.56 g of a beige-colored powder were obtained.

Proton NMR (DMSO-d6, δ): 2.00 (qd, J=11.5 Hz, J=3.0 Hz, 2H); 2.25 (dd, J=11.5 Hz, J=3.0 Hz, 2H), 3.10 (q, J=10.2 Hz, 2H), 3.30 (d, J=11 Hz, 2H), 3.50 (m, 1H), 7.26 (dd, J=5.0 Hz, 3.70 Hz), 7.78 (dd, J=3.5 Hz, J=1.1 Hz), 7.85 (dd, J=5.0 Hz, J=1.2 Hz).

MS m/z: 236 (M⁺+1)

2) Second Step: Synthesis of 2-chloro-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone

168 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperidinium hydrochloride obtained in step 1) above and 220 μl (3.1 eq.) of triethylamine were dissolved in 1 ml of dichloromethane and stirred at a temperature of −15° C. A solution of chloroacetyl chloride (40 μl, 1 eq.) in 1 ml of dichloromethane (CH₂Cl₂) was added dropwise to the resulting suspension. The resulting mixture was stirred at room temperature for 2 hours. 20 ml of dichloromethane were then added, and the resulting organic phase was washed with three times 50 ml of 5% hydrochloric acid and then dried over MgSO₄, filtered and evaporated. 2-Chloro-1-[4-(3-thiophen-2-yl[1,2,4]oxa-diazol-5-yl)piperid-1-yl]ethanone was obtained in the form of a white solid, in a yield of 95%.

Proton NMR (CDCl₃, δ): 2.00 (m, 2H); 2.19 (m, 2H); 3.08 (m, 1H); 3.29 (m, 2H); 3.95 (m, 1H); 4.12 (s, 2H, CH₂); 4.45 (m, 1H); 7.17 (dd, J=5.0 Hz, J=3.0 Hz, 1H); 7.53 (d, J=5.0 Hz, 1H); 7.80 (d, J=3.0 Hz, 1H).

MS m/z: 312 (M⁺+1)

3) Third Step: Synthesis of 2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone

The 312 mg (1 eq.) of 2-chloro-1-[4-(3-thiophen-2-yl[1,2,4]-oxadiazol-5-yl)piperid-1-yl]ethanone obtained above in the second step were dissolved in 1 ml of dimethylformamide (DMF) in a Schlenck tube under argon. 91 mg (1.4 eq.) of sodium azide were then added. The resulting suspension was then stirred at room temperature for 18 hours. The DMF was then evaporated off under reduced pressure, and the residue was taken up in 50 ml of ethyl acetate. The resulting organic phase was washed with 20 ml of KHSO₄ solution (0.1 N) and 20 ml of saturated NaHCO₃ solution and then with twice 20 ml of brine. The organic phase was then dried over MgSO₄, filtered and then evaporated under reduced pressure. 2-Azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone was obtained in the form of a translucent solid, in a yield of 80%.

Proton NMR (DMSO-d6, δ): 1.95 (m, 2H); 2.20 (m, 2H); 3.06 (m, 1H); 3.27 (m, 2H); 3.74 (m, 1H); 3.99 (s, 2H); 4.45 (m, 1H); 7.14 (dd, J=5.0 Hz, J=3.0 Hz, 1H); 7.50 (d, J=5.0 Hz, 1H); 7.78 (d, J=3.0 Hz, 1H).

MS m/z: 319 (M⁺+1)

The following compounds were synthesized according to the same protocol as that described above for the compound of formula (I-1):

2-azido-1-[4-(3-cyclopropyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 14)

MS m/z: 277 (M⁺+1)

¹H NMR (CDCl₃): δ 4.40 (m, 1H), 3.95 (s, 2H), 3.70 (m, 1H), 3.13 (m, 3H), 2.09 (m, 3H), 1.86 (m, 1H), 1.06 (m, 5H).

2-azido-1-[4-(3-pyrid-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 13)

MS m/z: 314 (M⁺+1)

2-azido-1-{4-[3-(3-chloro-2-methylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone (Compound 6)

MS m/z: 361 (M⁺+1)

¹H NMR (CDCl₃): δ 7.77 (dd, J=7.9 Hz J=1.4 Hz, 1H), 7.49 (dd, J=7.9 Hz J=1.4 Hz, 1H), 7.24 (t, J=7.9 Hz, 1H), 4.46 (m, 1H), 3.98 (s, 2H), 3.77 (m, 1H), 3.31 (m, 2H), 3.10 (m, 1H), 2.63 (s, 3H), 2.24 (m, 2H), 1.97 (m, 2H).

2-azido-1-[4-(3-pyrid-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone

MS m/z: (M⁺+1)

2-azido-1-{4-[3-(2-fluoro-5-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone

MS m/z: 399 (M⁺+1)

2-azido-1-{4-[3-(2,5-difluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (Compound 7)

MS m/z: 349 (M⁺+1)

¹H NMR (CDCl₃): δ 7.79 (m, 1H), 7.20 (m, 2H), 6.89 (d, J=8.0 Hz, 1H), 4.47 (m, 1H), 3.98 (s, 2H), 3.77 (m, 1H), 3.31 (m, 2H), 3.10 (m, 1H), 2.23 (m, 2H), 1.97 (m, 2H).

2-azido-1-{4-[3-(2-methoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (Compound 11)

MS m/z: 343 (M⁺+1)

¹H NMR (CDCl₃): δ 7.96 (dd, J=7.5 Hz J=1.6 Hz, 1H), 7.46 (ddd, J=9.3 Hz J=7.5 Hz J=1.9 Hz 1H), 7.06 (m, 2H), 4.42 (m, 1H), 3.95 (s, 2H), 3.73 (m, 1H), 3.29 (m, 2H), 3.08 (m, 1H), 2.19 (m, 2H), 1.95 (m, 2H).

¹³C NMR (CDCl₃): δ 179.22, 166.77, 165.57, 158.09, 132.44, 131.30, 120.70, 115.60, 111.69, 55.99, 50.80, 44.20, 41.20, 33.89, 29.45, 28.82.

2-azido-1-{4-[3-(2-chlorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (Compound 10)

MS m/z: 347 (M⁺+1)

¹H NMR (CDCl₃): δ 7.88 (dd, J=7.4 Hz J=2.2 Hz, 1H), 7.51 (dd, J=7.4 Hz J=1.6 Hz, 1H), 7.41 (td, J=7.4 Hz J=7.4 Hz J=2.2 Hz, 1H), 7.36 (dd, J=7.4 Hz J=7.4 Hz J=1.6 Hz, 1H), 4.42 (m, 1H), 3.96 (s, 2H), 3.73 (m, 1H), 3.30 (m, 2H), 3.08 (m, 1H), 2.19 (m, 2H), 1.95 (m, 2H).

2-azido-1-[4-(3-phenyl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 4)

MS m/z: 313 (M⁺+1)

2-azido-1-{4-[3-(3-trifluoromethoxyphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone

MS m/z: 397 (M⁺+1)

2-azido-1-{4-[3-(4-tert-butylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (Compound 9)

MS m/z: 369 (M⁺+1)

¹H NMR (CDCl₃): δ 7.99 (d, J=8.7 Hz, 2H), 7.50 (d, J=8.7 Hz, 2H), 4.45 (m, 1H), 3.98 (s, 2H), 3.75 (m, 1H), 3.28 (m, 2H), 3.10 (m, 1H), 2.21 (m, 2H), 1.98 (m, 2H), 1.35 (s, 9H).

¹³C NMR (CDCl₃): δ 181.00, 165.72, 154.92, 127.37, 126.70, 126.02, 123.90, 50.98, 44.37, 41.36, 35.14, 34.19, 31.33, 29.63, 28.96.

2-azido-1-{4-[3-(4-trifluoromethylphenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-ethanone (Compound 8)

MS m/z: 381 (M⁺+1)

¹H NMR (CDCl₃): δ 8.17 (d, J=8.2 Hz, 2H), 7.72 (d, J=8.2 Hz, 2H), 4.46 (m, 1H), 3.97 (s, 2H), 3.76 (m, 1H), 3.30 (m, 2H), 3.07 (m, 1H), 2.22 (m, 2H), 1.96 (m, 2H).

2-azido-1-[4-(3-benzo[1,3]-dioxol-5-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 12)

MS m/z: 357 (M⁺+1)

¹H NMR (CDCl₃): δ 7.61 (d, J=8.0 Hz, 1H), 7.49 (s, 1H), 6.89 (d, J=8.0 Hz, 1H), 6.03 (s, 2H), 4.43 (m, 1H), 3.97 (s, 2H), 3.73 (m, 1H), 3.26 (m, 2H), 3.09 (m, 1H), 2.19 (m, 1H), 1.95 (m, 2H).

¹³C NMR (CDCl₃): δ 180.24, 167.97, 165.61, 150.21, 148.15, 122.37, 120.44, 108.67, 107.41, 101.64, 50.93, 44.27, 41.24, 33.99, 29.45, 28.80.

2-azido-1-[4-(3-furan-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 2)

MS m/z: 303 (M⁺+1)

¹H NMR (CDCl₃): δ 7.61 (dd, J=1.8 Hz J=0.6 Hz, 1H), 7.12 (dd, J=3.3 Hz J=0.6 Hz, 1H), 6.56 (dd, J=3.3 Hz J=1.8 Hz, 1H), 4.45 (m, 1H), 3.97 (s, 2H), 3.75 (m, 1H), 3.27 (m, 2H), 3.05 (m, 1H), 2.18 (m, 2H), 1.95 (m, 2H).

2-azido-1-{4-[3-(4-fluorophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (Compound 5)

MS m/z: 331 (M⁺+1)

¹H NMR (CDCl₃): δ 8.07 (dd, J=8.8 Hz J=5.0 Hz, 2H), 7.17 (d, J=8.8 Hz, 2H), 4.46 (m, 1H), 3.98 (s, 2H), 3.76 (m, 1H), 3.29 (m, 2H), 3.10 (m, 1H), 2.22 (m, 2H), 1.97 (m, 2H).

2-azido-1-[4-(3-thiophen-3-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 3)

MS m/z: 319 (M⁺+1)

¹H NMR (CDCl₃): δ 8.05 (dd, J=3.0 Hz J=1.2 Hz, 1H), 7.63 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.43 (dd, J=5.1 Hz J=3.0 Hz, 1H), 4.46 (m, 1H), 3.98 (s, 2H), 3.77 (m, 1H), 3.28 (m, 2H), 3.09 (m, 1H), 2.21 (m, 2H), 1.98 (m, 2H).

2-azido-1-[4-(3-(6-methoxybenzothiazol-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 15)

¹H NMR (CDCl₃): δ 8.08 (d, J=9.0 Hz, 1H), 7.36 (d, J=2.5 Hz, 1H), 7.14 (dd, J=9.0 Hz J=2.5 Hz, 1H), 4.48 (m, 1H), 3.96 (s, 2H), 3.88 (s, 3H), 3.76 (m, 1H), 3.37 (m, 1H), 3.26 (m, 1H), 3.04 (m, 1H), 2.26 (m, 2H), 2.00 (m, 2H).

Example 3 Synthesis of 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone (Compound (I-2))

1) First Step: Synthesis of 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-(4-trimethylsilanyl[1,2,3]-triazol-1-yl)ethanone

159 mg (1 eq.) of the 2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxa-diazol-5-yl)piperid-1-yl]ethanone as obtained above in Example 2, 16 mg (0.1 eq.) of copper iodide and 52 μl (2.2 eq.) of ethynyltrimethylsilane were dissolved in 2 ml of acetonitrile in a Schlenck tube, under argon. The mixture was stirred at room temperature for 48 hours. The acetonitrile was evaporated off and the residue was then purified on silica gel (80/20 ethyl acetate/cyclohexane). 1-[4-(3-Thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-(4-trimethylsilanyl[1,2,3]triazol-1-yl)ethanone was obtained in the form of a greenish solid, in a yield of 41%.

Proton NMR (DMSO-d6, δ): 0.50 (s, 9H); 1.98 (m, 2H); 2.21 (m, 2H); 3.21 (m, 1H); 3.38 (m, 1H); 3.60 (m, 1H); 4.19 (m, 1H); 4.41 (m, 1H.); 5.84 (s, 2H); 7.17 (dd, J=5.0 Hz, J=3.0 Hz, 1H); 7.52 (d, J=5.0 Hz, 1H); 7.80 (d, J=3.0 Hz, 1H); 8.30 (brs, 1H)

MS m/z: 417 (M⁺+1)

2) Second Step: Synthesis of 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone

38 mg (1 eq.) of the 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-(4-trimethylsilanyl[1,2,3]triazol-1-yl)ethanone obtained above in the preceding step and 100 μl (1.05 eq.) of tetrabutylammonium fluoride were dissolved in 0.9 ml of THF in a sealed tube, and then refluxed for 1 hour. After cooling to room temperature, the THF was evaporated off and the residue was then purified on silica gel (90/10 CH₂Cl₂/methanol). 1-[4-(3-Thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone was obtained in the form of a pale yellow solid, in a yield of 48%.

Proton NMR (CDCl₃, δ): 1.94 (m, 2H); 2.21 (m, 2H); 3.11 (m, 1H); 3.30 (m, 1H); 3.41 (m, 1H); 4.01 (m, 1H); 4.41 (m, 1H); 5.36 (s, 2H); 7.16 (dd, J=5.0 Hz, J=3.0 Hz, 1H); 7.51 (d, J=5.0 Hz, 1H); 7.78 (d, J=3.0 Hz, 1H); 8.30 (brs, 2H).

MS m/z: 417 (M⁺+1)

Example 4 Synthesis of 4-iodo-N-(1-{2-oxo-2-[4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-1,2,3-triazol-4-ylmethyl)benzene-sulfonamide (Compound (I-4))

19 mg (59 μmol) of the 2-azido-1-[4-(3-thiophen-2-yl[1,2,4]-oxadiazol-5-yl)piperid-1-yl]ethanone (compound of formula (I-1)) as prepared above in Example 2 and 19 mg (59 μmol) of the alkyne were dissolved in 200 μl of acetonitrile, in a 1 ml Wheaton flask. 2 mg (5 mol %) of copper iodide dissolved in 200 μl of acetonitrile were then added to the solution. The reaction medium was stirred at room temperature for 18 hours. 21 mg of the expected product (I-4) were obtained.

¹H NMR (300 MHz, DMF-d7): 1.76 (m, 1H, H_(piperidine)); 2.04 (m, 1H, H_(piperidine)); 2.21 (m, 2H, H_(piperidine)); 3.00 (m, 1H, H_(piperidine)); 3.48 (m, 1H, H_(piperidine)); 3.51 (m, 1H, H_(piperidine)); 4.14 (m, 1H, H_(piperidine)); 4.24 (s, 2H); 4.42 (m, 1H, H_(piperidine)); 5.60 (m, 2H, CH₂); 7.33 (m, 1H, H_(thiophene)); 7.70 (m, 2H, H_(Ar)); 7.87 (m, 1H, H_(thiophene)); 7.94 (m, 2H, H_(thiophene), H_(triazole)); 8.09 (m, 2H, H_(Ar)); 8.20 (brs, 1H, NH).

¹³C NMR (75 MHz, DMF-d7): 30.00 (C_(piperidine)); 30.05 (C_(piperidine)); 33.84 (C_(piperidine)); 38.71 (CH₂); 41.00 (C_(piperidine)); 43.81 (C_(piperidine)); 50.89 (CH₂); 99.66 (C_(Ar)); 125.14 (CH_(triazole)); 128.12; 128.52 (CH_(thiophene)); 128.67 (2×CH_(Ar)); 129.91 (CH_(oxadiazole)); 130.45 (CH_(thiophene)); 138.44 (2×CH_(Ar)); 140.80 (C_(Ar)); 143.51; 164.17 (C_(thiophene)); 164.39 (C_(triazole)); 182.00.

MS m/z: 640 (M⁺+1)

The following compound was synthesized according to the same protocol as that described above for the compound of formula (I-4):

2-(2,2,2-trifluoroacetyl)-1,2,3,4-tetrahydroisoquinoline-7-sulfonic acid (1-{2-oxo-2-[4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-1,2,3-triazol-4-ylmethyl)amide

¹H NMR (300 MHz, DMF-d₇): 1.76 (m, 1H, H_(piperidine)); 2.00 (m, 1H, H_(piperidine)); 2.22 (m, 2H, H_(piperidine)); 3.00 (m, 1H, H_(piperidine)); 3.10 (m, 2H, H₃); 3.48 (m, 1H, H_(piperidine)); 3.51 (m, 1H, H₂₀); 3.97 (m, 2H, H₄); 4.14 (m, 1H, H_(piperidine)); 4.24 (m, 2H, CH₂); 4.42 (m, 1H, H_(piperidine)); 4.93 and 4.99 (2×s, 2H, H₁₁, cis and trans); 5.60 (m, 2H, H₁₆); 7.31-8.08 (m, 8H, 7H_(ar)+NH).

¹³C NMR (75 MHz, DMF-d₇): 30.00 (C_(piperidine). C₄); 30.05 (C_(piperidine)); 33.84 (C_(piperidine)); 38.81 (CH₂); 40.99 (C_(piperidine)); 43.00 (C_(THQ)); 43.78 (C_(piperidine)); 45.19 (C_(THQ)); 50.86 (CH₂); 125.17 (CH_(triazole)); 125.30; 128.12; 128.51; 129.60; 129.90; 130.45; 133.24; 138.88; 139.30; 143.69; 164.18; 164.40; 181.99.

MS m/z: 665 (M⁺+1)

Example 5 Synthesis of the t-butyl ester of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-ylmethyl)piperazine-1-carboxylic acid (Compound (I-5))

The starting halide (200 mg, 1 mmol) was introduced into a 10 ml round-bottomed flask, dissolved beforehand in 3 ml of absolute ethanol. The piperazine monosubstituted with a tert-butyloxy group (186 mg, 1 mmol) and K₂CO₃ (276 mg, 2 mmol) were then added. The mixture was refluxed overnight. After evaporating off the solvent, 30 ml of dichloromethane (DCM) were added to the reaction medium. The organic phase thus obtained was washed twice with 20 ml of H₂O and then once with 20 ml of saturated NaCl solution. The organic phase was then dried over MgSO₄, filtered and then evaporated.

Proton NMR (CDCl₃, δ): 7.74 (m, 1H); 7.44 (m, 1H); 7.16 (m, 1H); 3.89 (s, 2H); 3.45 (m, 4H); 2.58 (s, 4H); 1.37 (s, 9H).

MS m/z: 295 (M⁺-55).

Example 6 Synthesis of the t-butyl ester of 4-(5-thiophen-2-yl[1,2,4]oxadiazol-3-ylmethyl)piperazine-1-carboxylic acid (Compound I-6)

The starting halide (200 mg, 1 mmol) was introduced into a 10 ml round-bottomed flask, dissolved beforehand in 3 ml of absolute ethanol. The piperazine monosubstituted with a tert-butyloxy group (186 mg, 1 mmol) and K₂CO₃ (276 mg, 2 mmol) were then added. The mixture was refluxed overnight. After evaporating off the solvent, 30 ml of DCM were added to the reaction medium. The organic phase thus obtained was washed with twice 20 ml of H₂O and then once with 20 ml of saturated NaCl solution. The organic phase was then dried over MgSO₄, filtered and then evaporated.

Proton NMR (CDCl₃, δ): 7.86 (m, 1H); 7.59 (m, 1H); 7.14 (m); 3.74 (s, 2H); 3.45 (s, 4H); 2.55 (s, 4H); 1.38 (s, 9H).

MS m/z: 295 (M⁺−55)

Example 7 Synthesis of 2-azido-1-[4-(5-thiophen-2-yl-4H-[1,2,4]-triazol-3-yl)piperid-1-yl]ethanone (Compound I-14)

1) First Step: Synthesis of the t-butyl ester of 4-carbamoylpiperidine-1-carboxylic acid

2.56 g (20 mmol) of isonipecotamide were placed in a 50 ml round-bottomed flask and 10 ml of DCM, dried beforehand over magnesium sulfate, were then added. The isonipecotamide, which was partially soluble, remained in suspension. 5.62 ml (40 mmol; 2 eq.) of diethylamine (DIEA) were then added to the medium, along with 4.8 g (1.1 eq.) of di-tert-butyl dicarbonate dissolved beforehand in a further 10 ml of DCM. The medium was stirred at room temperature until the isonipecotamide was fully dissolved. The reaction was monitored by TLC to ensure, by staining with ninhydrin, the disappearance of the isonipecotamide from the medium.

At the end of the reaction, the organic phase was washed with basic aqueous 1M NaOH solution and then dried over magnesium sulfate and evaporated. 4.31 g of a white solid were obtained.

¹H NMR (CDCl₃): δ=6.01 (s, 2H), 4.12 (m, 2H), 2.74 (m, 2H), 2.32 (m, 1H), 1.82 (m, 2H), 1.62 (m, 2H), 1.51 (s, 9H).

MS m/z: 229 (M⁺+1)

2) Second Step: Synthesis of the t-butyl ester of 4-cyanopiperidine-1-carboxylic acid

2.05 g (9 mmol) of the t-butyl ester of 4-carbamoylpiperidine-1-carboxylic acid as obtained in the first step above were introduced into a Schlenck tube in the presence of 1.7 ml of DIEA (1-1 eq.). The medium was flushed under argon, and 18 ml of anhydrous THF were then added. The reaction medium was then cooled to a temperature of 0° C. and 1.38 ml of trifluoroacetic anhydride (1.1 eq.) were added dropwise. The medium then became totally clear. If the reaction is not complete after 1 hour, a further 0.5 equivalent of DIEA and then of trifluoroacetic anhydride are added. The reaction was monitored by TLC, staining with ninhydrin. At the end of the reaction, the organic phase was washed successively with aqueous solutions of 5% NaHCO₃, 0.1N KHSO₄ and saturated NaCl solution. The expected product was not visible under UV light. In the event of appearance of a UV-visible compound, a purification by flash chromatography in a gradient of eluent ranging from cyclohexane up to a 9/1 cyclohexane/ethyl acetate mixture may be performed. 1.1 g of a very pale yellow liquid that solidified after a few hours were obtained.

¹H NMR: (CDCl₃): 3.63 (m, 2H), 3.36 (m, 2H), 2.8 (m, 1H), 1.84 (m, 4H), 1.45 (s, 9H).

MS m/z: 211 (M⁺+1)

3) Third Step: Synthesis of the t-butyl ester of 4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperidine-1-carboxylic acid (compound I-7)

315 mg (1.5 mmol, 3 eq.) of the t-butyl ester of 4-cyano-piperidine-1-carboxylic acid obtained above in the second step were introduced into a Schlenck tube in the presence of 71 mg of thiophene-2-carboxylic hydrazide (0.5 mmol), 35 mg of K₂CO₃ (0.25 mmol; 0.5 eq.) and 2 ml of n-butanol. The medium was brought to a temperature of 150° C. and the reaction was monitored by TLC. At the end of the reaction, the reaction medium was evaporated, and the residue taken up in methanol and then neutralized by adding aqueous HCl solution. After evaporation, the compound was purified by flash chromatography in a 7/3 cyclohexane/ethyl acetate eluent, and then precipitated from diethyl ether. 102 mg of compound (I-7) as a white solid were thus obtained.

¹H NMR: (CDCl₃): δ=7.58 (dd, J=3.6 Hz, J=0.6 Hz, 1H), 7.41 (m, 1H), 7.07 (m, 1H), 4.12 (m, 2H), 2.9 (m, 3H), 1.94 (m, 2H), 1.68 (m, 2H), 1.42 (s, 9H).

MS m/z: 335 (M⁺+1)

4) Fourth and Fifth Steps: Synthesis of 2-azido-1-[4-(5-thiophen-2-yl-4H-[1,2,4]triazol-3-yl)piperid-1-yl]ethanone (compound I-14)

The deprotection and acetylation of this compound were performed as described previously in Example 2 above in the second and third steps of synthesis of compound (I-1), to give the expected compound (I-14).

MS m/z: 318 (M⁺+1)

Example 8 Synthesis of the allylic ester of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid (Compound 18)

90 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperidinium hydrochloride and 170 μl (3 eq.) of diisopropylethylamine were dissolved in 1.5 ml of dichloromethane. 39 μl (1.1 eq.) of allyl chloroformate were then added dropwise and the mixture was stirred for 2 hours at room temperature. The reaction medium was evaporated and 15 ml of ethyl acetate were added. The organic phase was washed with aqueous 1N sodium hydroxide solution (3×20 ml), with aqueous 1N hydrochloric acid solution (3×20 ml) and with saturated aqueous NaCl solution (20 ml) and then dried over MgSO₄ and concentrated under reduced pressure to give 92 mg (87%) of the expected compound.

¹H NMR analysis (CDCl₃): δ=7.76 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.48 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.12 (dd, J=5.0 Hz J=3.7 Hz, 1H), 5.92 (m, 1H), 5.29 (tdd, J=17.2 Hz J=2.9 Hz J=1.4 Hz, 1H), 5.20 (tdd, J=10.4 Hz J=2.9 Hz J=1.4 Hz, 1H), 4.59 (td, J=5.5 Hz J=1.4 Hz J=1.4 Hz, 1H), 4.16 (m, 2H), 4.1 (s, 2H), 3.16 (m, 1H), 3.05 (m, 2H), 2.12 (m, 2H), 1.91 (m, 2H)

¹³C NMR analysis (CDCl₃): δ=181.06, 164.35, 154.97, 132.98, 129.56, 129.28, 128.31, 127.97, 117.52, 66.14, 43.03, 34.31, 29.01

MS: m/z 320 (M+H⁺)

The following compounds, for which the various meanings of R are indicated, were also synthesized according to the same protocol:

2-phenoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 45)

MS: m/z 370 (M+H⁺)

¹H NMR (CDCl₃): δ=7.77 (dd, J=3.8 Hz J=1.2 Hz, 1H), 7.49 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.27 (dd, J=8.6 Hz J=1.2 Hz, 2H), 7.14 (dd, J=5.1 Hz J=3.8 Hz, 1H), 6.96 (m, 3H), 4.70 (s, 2H), 4.44 (m, 1H), 4.1 (m, 1H), 3.32 (m, 2H), 3.04 (m, 1H), 2.15 (m, 2H), 1.92 (m, 2H).

¹³C NMR (CDCl₃): δ=180.66, 166.54, 164.38, 157.79, 129.69, 129.64, 129.36, 128.21, 121.77, 114.5767.84, 44.51, 41.25, 34.20, 29.57, 28.83.

1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one (Compound 23)

MS: m/z 292 (M+H⁺)

¹H NMR (CDCl₃): δ=7.75 (dd, J=3.8 Hz J=1.2 Hz, 1H), 7.47 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.11 (dd, J=5.0 Hz J=3.8 Hz, 1H), 4.1 (m, 2H), 3.21 (m, 1H), 3.07 (m, 2H), 2.35 (q, J=7.5 Hz, 2H), 2.13 (m, 2H), 1.88 (m, 2H), 1.13 (t, J=7.5 Hz, 3H).

¹³C NMR (CDCl₃): δ=180.88, 172.29, 164.33, 129.59, 129.33, 128.21, 127.98, 34.37, 29.27, 26.49, 9.52.

3-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one (Compound 34)

MS: m/z 360 (M+H⁺)

¹H NMR (CDCl₃): δ=7.73 (dd, J=3.6 Hz J=1.2 Hz, 1H), 7.45 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.10 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.47 (m, 1H), 3.90 (m, 1H), 3.20 (m, 2H), 2.91 (m, 1H), 2.33 (t, J=7.8 Hz, 2H), 1.40-1.87 (m, 13H).

¹³C NMR (CDCl₃): δ=180.88, 171.83, 164.32, 129.57, 129.31, 128.22, 127.97, 39.84, 34.36, 32.65, 32.52, 31.62, 29.15, 25.13.

3,3-dimethyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one (Compound 26)

MS: m/z 334 (M+H⁺)

¹H NMR (CDCl₃): δ=7.74 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.46 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.11 (dd, J=5.0 Hz J=3.8 Hz, 1H), 4.51 (m, 1H), 3.98 (m, 1H), 3.19 (m, 1H), 3.00 (m, 2H), 2.27 (s, 2H), 2.13 (m, 2H), 1.88 (m, 2H), 1.03 (s, 9H).

¹³C NMR (CDCl₃): δ=180.90, 170.47, 164.33, 129.59, 129.31, 128.21, 127.98, 44.69, 34.35, 31.49, 30.06, 29.37.

2-thiophen-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 43)

MS: m/z 360 (M+H⁺)

¹H NMR (CDCl₃): δ=7.76 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.48 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.19 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.13 (dd, J=5.1 Hz J=3.7 Hz, 1H), 6.94 (dd, J=5.1 Hz J=3.5 Hz, 1H), 6.89 (dd, J=3.5 Hz J=1.2 Hz, 1H), 4.48 (m, 1H), 3.93 (m, 1H), 3.92 (s, 2H), 3.18 (m, 2H), 3.00 (m, 1H), 2.11 (m, 2H), 1.84 (m, 2H).

¹³C NMR (CDCl₃): δ=180.71, 168.44, 164.36, 136.33, 129.64, 129.38, 128.01, 126.94, 126, 09, 124.86, 45.35, 41.07, 35.24, 34.15, 29.29, 28.70.

3-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one (Compound 24)

MS: m/z 320 (M+H⁺)

¹H NMR (CDCl₃): δ=7.76 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.48 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.12 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.52 (m, 1H), 3.93 (m, 1H), 3.21 (m, 2H), 2.91 (m, 1H), 2.22 (d, J=6.4 Hz, 1H), 2.12 (m, 3H), 1.87 (m, 2H), 0.96 (d, J=6.4 Hz, 1H).

¹³C NMR (CDCl₃): δ=180.86, 176.47, 171.22, 164.31, 129.60, 129.33, 128.16, 127.97, 44.96, 42.06, 40.72, 34.34, 29.68, 29.01, 25.82, 22.70.

Example 9 Synthesis of 4-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-YL]pentan-1-one (Compound 25)

86 mg (2 eq.) of 4-methylvaleric acid, 141 mg (2 eq.) of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDCI) and 207 μl (4 eq.) of triethylamine were dissolved in 2 ml of dichloromethane. 100 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidinium hydrochloride were then added to the reaction medium, which was then stirred at room temperature for 24 hours. The reaction medium was evaporated under reduced pressure and the residue was taken up in 20 ml of ethyl acetate. The organic phase was washed with aqueous 1N sodium hydroxide solution (3×30 ml), with aqueous 1N hydrochloric acid solution (3×30 ml) and with saturated aqueous NaCl solution (30 ml) and then dried over MgSO₄ and concentrated under reduced pressure to give 102 mg (83%) of the expected compound.

¹H NMR (CDCl₃): δ=7.72 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.45 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.09 (dd, J=5.1 Hz J=3.7 Hz, 1H), 4.46 (m, 1H), 3.89 (m, 1H), 3.19 (m, 2H), 2.90 (m, 1H), 2.3 (t, J=8 Hz, 2H), 2.10 (m, 2H), 1.84 (m, 2H), 1.49 (m, 3H), 0.86 (d, J=6.4 Hz, 6H)

¹³C NMR (CDCl₃): δ=180.87, 171.86, 164.30, 129.58, 129.32, 128.19, 127, 98, 44.55, 40.73, 34.35, 34.21, 31.37, 29.27, 27.91, 22.39

MS: m/z 334 (M+H⁺)

The following compounds, for which the various meanings of R are indicated, were synthesized according to the same protocol:

2-bicyclo[2.2.1]hept-2-yl-1-[4-(3-thiophen-2-YL[1,2,4]oxadiazol-5-YL)piperid-1-yl]ethanone (Compound 40)

MS: m/z 372 (M+H⁺)

¹H NMR (CDCl₃): δ 7.71 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.43 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.07 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.46 (m, 1H), δ 3.87 (m, 1H), 3.17 (m, 2H), 2.86 (m, 1H), 1.81-2.31 (m, 11H), 1.23-1.42 (m, 4H), 1 (m, 2H).

¹³C NMR (CDCl₃): δ=180.87, 171.06, 164.27, 129.58, 129.32, 128.16, 127.97, 44.79, 41.14, 40.65, 40.04, 38.58, 38.02, 36.75, 35.30, 34.33, 29.86, 29.65, 28.99, 28.55.

2-cyclopropyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 33)

MS: m/z 318 (M+H⁺)

¹H NMR (CD₂Cl₂): δ=7.80 (dd, J=3.9 Hz J=1.2 Hz, 1H), 7.56 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.20 (dd, J=5.1 Hz J=3.9 Hz, 1H), 4.55 (m, 1H), 3.93 (m, 1H), 3.27 (m, 2H), 2.94 (m, 1H), 2.27 (d, J=7.2 Hz, 2H), 2.21 (m, 2H), 1.91 (m, 2H), 1.06 (m, 1H), 0.58 (m, 2H), 0.20 (m, 2H).

3-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one (Compound 38)

MS: m/z 374 (M+H⁺)

¹H NMR (CDCl₃): δ=7.71 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.44 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.08 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.46 (m, 1H), 3.87 (m, 1H), 3.18 (m, 2H), 2.86 (m, 1H), 1.45-2.35 (m, 19H).

¹³C NMR (CDCl₃): δ=180.87, 172.12, 164.228, 129.58, 129.32, 128.17, 121.97, 44.75, 40.71, 37.44, 34.33, 33.10, 32.80, 30.90, 29.63, 28.94, 26.52, 26.22.

2-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 41)

MS: m/z 354 (M+H⁺)

¹H NMR (CDCl₃): δ=7.73 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.45 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.21-7.32 (m, 5H), 7.10 (dd, J=5.1 Hz J=3.7 Hz, 1H), 4.47 (m, 1H), 3.86 (m, 1H), 3.73 (s, 2H), 3.13 (m, 2H), 2.94 (m, 1H), 1.6-2.12 (m, 4H).

¹³C NMR (CDCl₃): δ=180.79, 169.44, 164.30, 134.95, 129.62, 129.38, 128.82, 128.57, 128.19, 128.03, 126.90, 45.18, 41.08, 40.88, 34.15, 29.23, 28.77

3-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one (Compound 42)

MS: m/z 368 (M+H⁺)

¹H NMR (CDCl₃): δ=7.76 (dd, J=3.6 Hz J=1.2 Hz, 1H), 7.46 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.18-7.30 (m, 5H), 7.12 (dd, J=5.1 Hz J=3.6 Hz, 1H), 4.51 (m, 1H), 3.80 (m, 1H), 3.13 (m, 2H), 2.97 (t, J=7.9 Hz, 1H), 2.92 (m, 1H), 2.64 (t, J=7.9 Hz, 2H), 2.06 (m, 2H), 2.64 (t, J=7.9 Hz, 2H), 1.74 (m, 2H).

¹³C NMR (CDCl₃): δ 180.83, 170.69, 164.34, 141.14, 129.59, 129.35, 128.57, 128.47, 128.30, 126.27, 44.68, 40.81, 35.03, 34.28, 31.59, 29.41, 28.90.

2-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 37)

MS: m/z 360 (M+H⁺)

¹H NMR (CDCl₃): δ=7.69 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.42 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.06 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.44 (m, 1H), 3.87 (m, 1H), 3.17 (m, 2H), 2.88 (m, 1H), 2.17 (d, J=6.7 Hz, 2H), 2.09 (m, J=6.7 Hz J=2.7 Hz, 3H), 1.59-1.83 (m, 12H).

¹³C NMR (CDCl₃): δ=180.84, 171.29, 164.24, 129.60, 129.34, 128.07, 127.95, 45.06, 41.97, 40.67, 35.17, 34.25, 33.30, 32.95, 29.64, 28.96, 26.03.

2-cyclopent-2-enyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]-ethanone (Compound 36)

MS: m/z 344 (M+H⁺)

¹H NMR (CDCl₃): δ=7.71 (dd, J=3.7 Hz J=1.1 Hz, 1H), 7.43 (dd, J=5.0 Hz J=1.1 Hz, 1H), 7.08 (dd, J=5.0 Hz J=3.7 Hz, 1H), 5.69 (m, 1H), 5.63 (m, 1H), 4.47 (m, 1H), 3.87 (m, 1H), 3.16 (m, 2H), 3.07 (m, 1H), 2.84 (m, 1H), 2.30 (m, 4H), 2.09 (m, 3H), 1.81 (m, 2H), 1.39 (m, 1H).

¹³C NMR (CDCl₃): δ=180.87, 170.73, 164.28, 134.23, 131.27, 129.59, 129.33, 128.16, 127.97, 44.73, 42.12, 40.66, 39.23, 34.32, 31.79, 29.94, 29.61, 28.97.

2-(4-methylcyclohexyl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 39)

MS: m/z 374 (M+H⁺)

¹H NMR (CDCl₃): δ=7.70 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.42 (dd, J=5.1 Hz J=1.2 Hz, 1H), 7.07 (dd, J=5.1 Hz J=3.7 Hz, 1H), 4.45 (m, 1H), 3.88 (m, 1H), 3.17 (m, 2H), 2.86 (m, 1H), 2.26 (d, J=7.2 Hz, 2H), 1.18-2.17 (m, 16H).

3-tert-butoxy-1-[4-(3-thiophen-2-YL[1,2,4]oxadiazol-5-YL)piperid-1-Yl]propan-1-one (Compound 30)

MS: m/z 364 (M+H⁺)

¹H NMR (CDCl₃): δ 7.70 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.43 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.07 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.45 (m, 1H), 3.94 (m, 1H), 3.62 (t, J=6.8 Hz, 2H), 3.17 (m, 2H), 2.87 (m, 1H), 2.53 (q, J=6.8 Hz, 2H), 2.07 (m, 2H), 1.81 (m, 2H), 1.12 (s, 9H).

¹³C NMR (CDCl₃): δ=180.90, 170.18, 164.27, 129.54, 129.29, 128.20, 127.94, 73.10, 58.50, 44.96, 40.71, 34.29, 34.29, 29.56, 28.95, 27.47.

2-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 35)

MS: m/z 346 (M+H⁺)

¹H NMR (CDCl₃): δ=7.70 (dd, J=3.6 Hz J=1.2 Hz, 1H), 7.43 (dd, J=5.0 Hz J=1.2 Hz, 1H), 7.08 (dd, J=5.0 Hz J=3.6 Hz, 1H), 4.47 (m, 1H), 3.89 (m, 1H), 3.17 (m, 2H), 2.86 (m, 1H), 2.32 (d, J=7.5 Hz, 2H), 2.10 (m, 2H), 1.80 (m, 4H), 1.54 (m, 4H), 1.11 (m, 2H).

¹³C NMR (CDCl₃): δ=180.96, 171.36, 164.34, 129.63, 129.37, 128.26, 128.02, 44.88, 40.70, 39.25, 36.79, 34.41, 32.75, 29.71, 29.06, 25.00.

4,4,4-trifluoro-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one (Compound 27)

MS: m/z 346 (M+H⁺)

¹H NMR (CDCl₃): δ=7.74 (dd, J=3.7 Hz J=1.1 Hz, 1H), 7.47 (dd, J=5.0 Hz J=1.1 Hz, 1H), 7.11 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.45 (m, 1H), 3.86 (m, 1H), 3.23 (m, 2H), 2.96 (m, 1H), 2.52 (m, 4H), 2.13 (m, 2H), 1.88 (m, 2H).

¹³C NMR (CDCl₃): δ=180.66, 168.07, 164.34, 129.63, 129.36, 128.89, 125.24, 44.38, 40.98, 34.15, 29.74, 29.38, 28.81, 25.87.

1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-en-1-one (Compound 20)

MS: m/z 318 (M+H⁺)

¹H NMR (CDCl₃): δ 7.74 (dd, J=3.7 Hz J=1.1 Hz, 1H), 7.47 (dd, J=5.0 Hz J=1.1 Hz, 1H), 7.12 (dd, J=5.0 Hz J=3.7 Hz, 1H), 5.80 (m, 1H), 5.00 (m, 2H), 4.50 (m, 1H), 3.90 (m, 1H), 3.23 (m, 2H), 2.92 (m, 1H), 2.42 (m, 4H), 2.13 (m, 2H), 1.87 (m, 2H).

¹³C NMR (CDCl₃): δ=180.84, 170.69, 164.35, 137.38, 129.60, 129.33, 128.22, 127.99, 115.35, 44.63, 40.75, 34.35, 32.53, 29.61, 29.29, 28.98

1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-yn-1-one (Compound 21)

MS: m/z 346 (M+H⁺)

¹H NMR (CD₂Cl₂): δ=7.80 (dd, J=3.7 Hz J=1.2 Hz, 1H), 7.57 (dd, J=4.8 Hz J=1.2 Hz, 1H), 7.20 (dd, J=4.8 Hz J=3.7 Hz, 1H), 4.52 (m, 1H), 3.95 (m, 1H), 3.26 (m, 2H), 2.95 (m, 1H), 2.60 (m, 4H), 2.19 (m, 2H), 2.04 (m, 1H), 1.93 (m, 2H).

3-oxo-3-[4-(3-thiophen-2-YL[1,2,4]oxadiazol-5-yl)piperid-1-yl]propionitrile (Compound 22)

MS: m/z 303 (M+H⁺)

¹H NMR (CD₂Cl₂): δ=7.81 (dd, J=3.6 Hz J=1.2 Hz, 1H), 7.58 (dd, J=4.8 Hz J=1.2 Hz, 1H), 7.21 (dd, J=4.8 Hz J=3.6 Hz, 1H), 4.46 (m, 1H), 3.79 (m, 1H), 3.58 (s, 2H), 3.30 (m, 2H), 3.09 (m, 1H), 2.25 (m, 2H), 2.00 (m, 2H).

2-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 28)

MS: m/z 308 (M+H⁺)

¹H NMR (CD₂Cl₂): δ=7.81 (dd, J=3.9 Hz J=1.2 Hz, 1H), 7.57 (dd, J=4.8 Hz J=1.2 Hz, 1H), 7.21 (dd, J=4.8 Hz J=3.9 Hz, 1H), 4.48 (m, 1H), 4.12 (s, 2H), 3.95 (m, 1H), 3.43 (s, 3H), 3.29 (m, 2H), 2.97 (m, 1H), 2.19 (m, 2H), 1.89 (m, 2H).

3-methoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one (Compound 29)

MS: m/z 322 (M+H⁺)

Example 10 Synthesis of 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperid-1-yl]ethanone (Compound 17)

50 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperidinium hydrochloride and 77 μl (3 eq.) of diisopropylethylamine were dissolved in 1 ml of dichloromethane. 39 μl (1.2 eq.) of acetic anhydride were added dropwise and the reaction medium was stirred for 2 hours at room temperature. The reaction medium was evaporated and the residue was taken up in 15 ml of ethyl acetate. The organic phase was washed with aqueous 1N sodium hydroxide solution (3×30 ml), with aqueous 1N hydrochloric acid solution (3×30 ml) and with saturated aqueous NaCl solution (30 ml), dried over MgSO₄ and concentrated under reduced pressure to give 41 mg (98%) of the expected compound.

¹H NMR (CDCl₃): δ=7.76 (dd, J=3.7 Hz J=1.1 Hz, 1H), 7.48 (dd, J=5.0 Hz J=1.1 Hz, 1H), 7.13 (dd, J=5.0 Hz J=3.7 Hz, 1H), 4.48 (m, 1H), 3.93 (m, 1H), 3.23 (m, 2H), 2.94 (m, 1H), 2.12 (m, 5H), 1.90 (m, 2H)

¹³C NMR (CDCl₃): δ 180.79, 169.09, 164.37, 129.61, 129.35, 128.21, 128.00, 34.25, 29.70, 21.37

MS: m/z 278 (M+H⁺)

The following compounds, for which the various meanings of R are indicated, were synthesized according to the same protocol:

4-oxo-4-[4-(3-thiophen-2-YL[1,2,4]oxadiazol-5-YL)piperid-1-yl]butyric acid (Compound 31)

MS: m/z 336 (M+H⁺)

¹H NMR (CDCl₃): δ=7.77 (d, J=3.6 Hz, 1H), 7.50 (d, J=4.9 Hz, 1H), 7.15 (dd, J=4.9 Hz J=3.6 Hz, 1H), 4.48 (m, 1H), 3.95 (m, 1H), 3.27 (m, 2H), 3.02 (m, 1H), 2.72 (s, 4H), 2.17 (m, 2H), 1.96 (m, 2H).

¹³C NMR (CDCl₃): δ 180.77, 176.86, 170.22, 164.40, 129.68, 129.39, 128.15, 128.02, 34.19, 29.48, 27.97.

5-oxo-5-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentanoic acid (Compound 32)

MS: m/z 350 (M+H⁺)

¹H NMR (CDCl₃): δ=7.78 (dd, J=3.7 Hz J=1.1 Hz, 1H), δ 7.50 (dd, J=5.0 Hz J=1.1 Hz, 1H), δ 7.15 (dd, J=5.0 Hz J=3.7 Hz, 1H), δ 4.51 (m, 1H), δ 3.93 (m, 1H), δ 3.26 (m, 2H), δ 2.97 (m, 1H), δ 2.48 (m, J=7 Hz, 4H), δ 2.18 (m, 2H), δ 1.95 (m, 4H).

¹³C NMR (CDCl₃): δ 180.76, 177.70, 171.12, 164.35, 129.66, 129.38, 128.16, 128.01, 34.24, 33.18, 32.14, 20.26.

Example 11 Synthesis of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperidine-1-carboxylic acid phenylamide (Compound 48)

40 μl (1 eq.) of phenyl isocyanate were added to a solution of 100 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidinium hydrochloride in 0.6 ml of pyridine. The reaction medium was stirred at room temperature overnight and then evaporated under reduced pressure. The residue obtained was chromatograph on a thick layer of silica (eluent: CH₂Cl₂/MeOH (95/5; v/v)). After evaporating off the solvent, 48 mg (37%) of the expected compound were obtained.

¹H NMR (CD₂Cl₂): δ=7.80 (dd, 1H, J=3.69 Hz, J=1.21 Hz), 7.56 (dd, 1H, J=5.04 Hz, J=1.21 Hz), 7.32 (m, 4H), 7.19 (dd, 1H, J=5.04 Hz, J=3.68 Hz), 7.04 (m, 1H), 4.08 (m, 2H), 3.14 (m, 3H), 2.21 (m, 2H), 2.02 (m, 2H).

MS: m/z 355 (M+H⁺)

The following compounds were synthesized according to the same protocol, starting with the corresponding isocyanate or isothiocyanate:

4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carbothioic acid phenylamide (Compound 49)

MS: m/z 371 (M+H⁺)

¹H NMR (CD₂Cl₂): δ 7.76 (dd, 1H, J=3.68 Hz, J=1.21 Hz), 7.74-7.79 (m, 1H), 7.56 (dd, 1H, J=5.04 Hz, J=1.21 Hz), 7.34 (m, 2H), 7.16 (m, 4H), 4.51 (m, 2H), 3.31 (m, 3H), 2.15 (m, 2H), 1.95 (m, 2H).

4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid thiophen-2-ylamide (Compound 50)

MS: m/z 361 (M+H⁺)

¹H NMR (CD₂Cl₂): δ 7.79 (dd, 1H, J=3.61 Hz, J=1.21 Hz), 7.55 (dd, 1H, J=5.02 Hz, J=1.21 Hz), 7.18 (dd, 2H, J=5.07 Hz, J=3.67 Hz), 7.15-7.18 (m, 1H), 4.05 (m, 2H), 3.14 (m, 3H), 2.20 (m, 2H), 1.92 (m, 2H).

4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carbothioic acid cyclopropylamide (Compound 52)

MS: m/z 335 (M+H⁺)

¹H NMR (MeOD): δ 7.78 (dd, 1H, J=3.71 Hz, J=1.17 Hz), 7.66 (dd, 1H, J=5.04 Hz, J=1.17 Hz), 7.18 (dd, 1H, J=4.99 Hz, J=3.63 Hz), 4.61 (m, 2H), 3.27 (m, 3H), 2.96 (m, 1H), 2.13 (m, 2H), 1.81 (m, 2H), 0.76 (m, 2H), 0.60 (m, 2H).

Example 12 Synthesis of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine-1-carboxylic acid cyclopropylamide (Compound 51)

54.60 mg (1 eq.) of triphosgene were added to a suspension of 150 mg (3 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidinium hydrochloride and 102.63 μl (4 eq.) of triethylamine in 2 ml of toluene. The reaction medium was stirred overnight at room temperature and then filtered. The filtrate thus collected was concentrated under reduced pressure. The residue obtained was taken up in 2 ml of dichloromethane, followed by addition of 77 μL (1 eq.) of triethylamine and 77.44 μl (2 eq.) of cyclopropylamine. The reaction medium was stirred for 20 hours at room temperature and then concentrated to dryness. The residue was chromatograph on a thick layer of silica (eluent: CH₂Cl₂/MeOH (95/5; v/v)) to give 80 mg (45%) of the expected product.

¹H NMR (MeOD, δ): 7.76 (dd, 1H, J=3.67 Hz, J=1.05 Hz), 7.64 (dd, 1H, J=5.09 Hz, J=1.01 Hz), 7.16 (dd, 1H, J=4.98 Hz, J=3.77 Hz), 3.98 (m, 2H), 3.22 (m, 1H), 2.96 (m, 2H), 2.50 (m, 1H), 2.07 (m, 2H), 1.76 (m, 2H), 0.63 (m, 2H), 0.44 (m, 2H).

MS: m/z 319 (M+H⁺)

Example 13 Synthesis of 1-phenylmethanesulfonyl-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine (Compound 53)

140.30 mg (2 eq.) of benzenesulfonyl chloride were added to a solution of 100 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)-piperidinium hydrochloride and 102.63 μl (2 eq.) of triethylamine in 1.5 ml of dichloroethane. The mixture was stirred overnight at room temperature and then evaporated under reduced pressure. The residue was chromatograph on a thick layer of silica (eluent: CH₂Cl₂) to give, after evaporating off the solvent, 74 mg (52%) of the expected product.

¹H NMR (CD₂Cl₂ δ): 7.78 (dd, 1H, J=3.7 Hz, J=1.17 Hz), 7.56 (dd, 1H, J=5.04 Hz, J=1.15 Hz), 7.40 (m, 5H), 7.17 (dd, 1H, J=5.01 Hz, J=3.67 Hz), 4.26 (s, 2H), 3.60 (m, 2H), 3.06 (m, 1H), 2.86 (m, 2H), 2.09 (m, 2H), 1.84 (m, 2H).

MS: m/z 390 (M+H⁺)

The following compound was synthesized according to the same protocol:

1-(Thiophene-3-sulfonyl)-4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidine

MS: m/z 382 (M+H⁺)

Example 14 Synthesis of phenyl[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]methanone (Compound 54)

67.40 mg (1 eq.) of benzoic acid, 106 mg (1 eq.) of EDCI and 165 μl (2 eq.) of triethylamine were dissolved in 2 ml of dichloromethane. 150 mg (1 eq.) of 4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperidinium hydrochloride dissolved in 2 ml of dichloromethane and 165 μl (2 eq.) of triethylamine were added to the reaction medium, which was stirred at room temperature overnight. The reaction medium was evaporated under reduced pressure and the residue was chromatographed on a thick layer (eluent: CH₂Cl₂/MeOH (98/2: v/v)) to give 98 mg (52%) of the expected product.

¹H NMR (CD₂Cl₂, δ): 7.76 (dd, 1H, J=3.40 Hz, J=1.10 Hz), 7.52 (dd, 1H, J=4.88 Hz, J=1.09 Hz), 7.40 (m, 5H), 7.15 (dd, 1H, J=5.34 Hz, J=3.86 Hz), 4.55-4.65 (m, 1H), 3.80-3.90 (m, 1H), 3.24 (m, 1H), 3.10 (m, 2H), 2.05-2.30 (m, 2H), 1.80-2.00 (m, 2H).

MS: m/z 340 (M+H⁺)

The following compounds were synthesized according to the same protocol:

2-thiophen-3-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone (Compound 60)

¹H NMR (MeOD, δ): 7.77 (dd, 1H, J=3.7 Hz, J=1.21 Hz), 7.65 (dd, 1H, J=5.06 Hz, J=1.21 Hz), 7.39 (dd, 1H, J=4.96 Hz, J=2.96 Hz), 7.18 (m, 2H), 7.03 (dd, 1H, J=4.96 Hz, J=1.30 Hz), 3.82 (s, 2H), 3.25-3.35 (m, 2H), 2.95 (m, 1H), 2.02 (m, 2H), 1.60 (m, 2H).

MS: m/z 360 (M+H⁺)

2-(2-aminothiazol-4-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone

MS: m/z 376 (M+H⁺)

Example 15 Synthesis of 1-{4-[3-(2-aminothiazol-5-yl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}-2-cyclopropylethanone

1) First Step: Synthesis of 2-aminothiazole-5-carbonitrile

6.17 ml (1 eq.) of dibromine were added to a solution of 10.10 ml (1 eq.) of 3-methoxyacrylonitrile in 35 ml of cold acetonitrile at a temperature of 0° C. The medium was stirred for 20 minutes and then 80 ml of distilled water, cooled to 5° C., were added thereto. The mixture was stirred vigorously for 1 hour, and 8.88 g (0.9 eq.) of sodium acetate were then added. After stirring for 15 minutes, 10.07 g (1.1 eq.) of thiourea were added and the reaction medium was stirred at a temperature of between 0° C. and 10° C. for 2 hours. 5.92 g (0.6 eq.) of sodium acetate were then added and the reaction medium was maintained at 60° C. for 3 hours. The temperature of the medium was lowered to 10° C. and sodium hydroxide (10N) was added thereto until a pH of 4 was obtained. The precipitate formed was filtered off by suction, washed with water and purified using charcoal in acetone at 50° C. (1 hour 30 minutes). The mixture was filtered while hot and the collected filtrate was concentrated under reduced pressure. The residue obtained was washed with heptane and then with a heptane/acetone mixture (2/1; v/v) to give 12.5 g (83%) of the expected product.

¹H NMR (DMSO-d₆, 6): 7.82 (s, 1H), 8.05-8.20 (m, 2H).

MS: m/z 126 (M⁺+1).

2) Second Step: Synthesis of 2-amino-N-hydroxythiazole-5-carboxamidine

4.42 ml (1.6 eq.) of DIEA and then 1.66 g (1.5 eq.) of hydroxylamine hydrochloride were added to a solution of 2 g (1 eq.) of the carbonitrile, obtained above in the preceding step, in 26.5 ml of ethanol. The medium was refluxed for 4 hours and then concentrated to dryness. The residue obtained was taken up in water and the aqueous phase was extracted twice with ethyl acetate. The combined organic phases were dried over MgSO₄ and concentrated to dryness to give 1.77 g (70%) of the expected product.

¹H NMR (DMSO-d₆, δ): 5.70-5.90 (m, 2H), 7.00-7.20 (m, 2H), 7.35 (s, 1H), 9.41 (s, 1H).

MS: m/z 159 (M⁺+1).

The following compound was also synthesized according to the same protocol:

3-dibenzylamino-N-hydroxybenzamidine

¹H NMR (MeOD, δ): 6.75 (m, 14H), 4.69 (m, 4H).

MS m/z: 332 (M⁺+1).

3) Third Step: Synthesis of the tert-butyl ester of 4-[3-(2-aminothiazol-5-yl)-[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

0.725 g (1 eq.) of the mono-tert-butyl ester of piperidine-1,4-dicarboxylic acid, 1.20 g (1 eq.) of O-benzotriazol-1-yl-N,N,N′,N′-tetramethyl-uronium hexafluorophosphate (HBTU), 0.097 g (0.2 eq.) of 1-hydroxy-benzotriazole hydrate (HOBT) and 2.75 ml (5 eq.) of ethyldiisopropylamine in 50 ml of dimethylformamide (DMF) were stirred for 1 minute. 0.500 g (1 eq.) of 2-amino-N-hydroxythiazole-5-carboxamidine was then added to the suspension. The resulting mixture was stirred at room temperature overnight. The mixture was then concentrated to dryness and the residue obtained was taken up in ethyl acetate and then washed successively with water, with saturated aqueous NaCl solution and with saturated NaHCO₃ solution. The combined organic phases were dried over MgSO₄ and concentrated to dryness. The residue obtained was taken up in 15 ml of DMF and stirred at reflux for 2 hours. The medium was concentrated to dryness. The residue was taken up in ethyl acetate and washed with 5% NaHCO₃ solution, and then with saturated aqueous NaCl solution. The combined organic phases were dried over MgSO₄ and evaporated under reduced pressure. The residue was chromatographed on a thick layer (eluent: CH₂Cl₂/MeOH (95/5 v/v)) to give 80 mg (7%) of the expected product.

¹H NMR (CD₂Cl₂, δ): 7.75 (s, 1H), 5.50-5.70 (m, 2H), 4.09 (m, 2H), 3.09 (m, 1H), 2.92 (m, 2H), 2.06 (m, 2H), 1.47 (m, 2H), 1.47 (s, 9H).

MS m/z: 352 (M⁺+1).

The following compound was also synthesized according to the same protocol:

tert-Butyl ester of 4-[3-(3-dibenzylaminophenyl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic acid

¹H NMR (CD₂Cl₂, δ): 7.47 (m, 1H), 7.25 (m, 10H), 6.86 (m, 1H), 4.76 (s, 4H), 4.08 (m, 2H), 3.12 (m, 1H), 2.94 (m, 2H), 2.05 (m, 2H), 1.77 (m, 2H), 1.48 (s, 9H).

MS m/z: 525 (M⁺+1).

4) Fourth Step: Synthesis of 5-(5-piperid-4-yl[1,2,4]oxadiazol-3-yl)thiazol-2-yl-amine dihydrochloride

80 mg (1 eq.) of the tert-butyl ester of 4-[3-(2-aminothiazol-5-yl)[1,2,4]oxadiazol-5-yl]piperidine-1-carboxylic were dissolved in 2 ml of absolute ethanol. A 4N solution of hydrogen chloride in dioxane (0.57 ml) was added thereto. The reaction medium was stirred overnight at room temperature and then concentrated to dryness to give 70 mg (95%) of the expected product.

¹H NMR (MeOD, δ): 7.98 (s, 1H), 3.48 (m, 3H), 3.19 (m, 2H), 2.39 (m, 2H), 2.07 (m, 2H).

¹³C NMR (MeOD, δ): 181.13, 171.01, 161.23, 129.29, 110.57, 42.54, 42.53, 31.45, 25.53, 25.52.

MS m/z: 252 (M⁺+1).

The following compound was also synthesized according to the same protocol:

Dibenzyl[3-(5-piperid-4-yl[1,2,4]oxadiazol-3-yl)phenyl]amine hydrochloride

¹H NMR (MeOD, δ): 7.93 (m, 2H), 7.52 (m, 2H), 7.27 (m, 10H), 5.03 (s, 4H), 3.48 (m, 3H), 3.19 (m, 2H), 2.37 (m, 2H), 2.11 (m, 2H).

MS m/z: 426 (M⁺+1).

5) Fifth Step: Synthesis of 1-{4-[3-(2-aminothiazol-5-yl)[1,2,4]oxadiazol-5-yl]-piperid-1-yl}-2-cyclopropylethanone

18.52 mg (1 eq.) of cyclopropylacetic acid, 35.47 mg (1 eq.) of EDCI and 26 μl (1 eq.) of triethylamine were dissolved in 200 μl of dichloromethane. The mixture was stirred for 10 minutes, and the 5-(5-piperid-4-yl[1,2,4]oxadiazol-3-yl)thiazol-2-ylamine hydrochloride, obtained above in the preceding step, was dissolved in 2 ml of CH₂Cl₂, and 52 μl (2 eq.) of Et₃N were then added. The reaction medium was stirred at room temperature overnight and then concentrated to dryness. The residue obtained was chromatographed on a thick layer of silica (eluent: CH₂Cl₂/MeOH (95/5 v/v)) to give 47 mg (76%) of the expected product.

¹H NMR (MeOD, δ): 7.68 (s, 1H), 4.47 (m, 1H), 3.99 (m, 1H), 3.32 (m, 2H), 2.99 (m, 1H), 2.36 (d, 2H, J=6.87 Hz), 2.15 (m, 2H), 1.74 (m, 2H), 0.98 (m, 1H), 0.57 (m, 2H), 0.19 (m, 2H).

¹³C NMR (MeOD, δ): 180.96, 172.27, 162.86, 142.02, 128.55, 127.83, 44.79, 40.59, 37.83, 33.88, 29.44, 28.68, 6.90, 3.70, 3.59.

MS m/z: 334 (M⁺+1).

The following compound was also synthesized according to the same protocol:

2-cyclopropyl-1-{4-[3-(3-dibenzylaminophenyl)[1,2,4]oxadiazol-5-yl]piperid-1-yl}ethanone (compound 57)

¹H NMR (CD₂Cl₂, δ): 6.88 (m, 1H), 7.24 (m, 12H), 7.48 (m, 1H), 4.75 (s, 2H), 4.46 (m, 1H), 3.87 (m, 1H), 3.21 (m, 1H), 2.93 (m, 1H), 2.28 (d, 2H, J=6.68 Hz), 2.13 (m, 2H), 1.80 (m, 1H), 0.86 (m, 1H), 0.53 (m, 2H), 018 (m, 2H).

MS m/z: 507 (M⁺+1).

Example 16 Demonstration of the Potentiating Effect on ETH Activity by the Compound of Formula (I-3)

The aim of this example is to demonstrate the increase in sensitivity to ETH of Mycobacterium tuberculosis bacteria, when this antibiotic is combined with a compound of formula (I). In this example, the compound of formula (I-3) as prepared above in Example 1 was used.

1) Materials and Methods

The ability of the compound of formula (I-3) to increase the sensitivity to ETH of the test strain was studied after preparation of an agar gel inoculated, in supercooled state, with about 10⁸ Mycobacterium tuberculosis bacilli (strain H37RV), followed by pouring into Petri dishes.

Holes were made in the thickness of the cooled gel using a sample punch, in order to form wells capable of receiving the antibiotic ETH and/or the compound of formula (I-3), into the bottom of which wells a small thickness of sterile gel is poured beforehand so as to avoid any contact of the test compounds with the plastic base of the Petri dish.

The test compounds are then placed in the bottom of the wells.

Three Petri dishes A, B and C were thus prepared:

-   -   Dish A: Hole A1: no product (control)         -   Hole A2: 20 nmol of compound of formula (I-3)     -   Dish B: Hole B1: 2 μg of ETH         -   Hole B2: 4 μg of ETH     -   Dish C: Hole C1: 2 μg of ETH+20 nmol of compound of formula         (I-3)         -   Hole C2: 4 μg of ETH+20 nmol of compound of formula (I-3)

Dishes A, B and C were then left for three weeks in an oven at a temperature of 37° C., and the regions of inhibition of mycobacterial growth around the wells were then observed.

2) Results

The results obtained are given in the attached FIG. 1.

In this figure, it is seen that, at the test doses, the compound of formula (I-3) does not show any bacterial toxicity (no inhibition of growth around well A2). Dish B shows that the deposition of 2 μg (hole B1) or 4 μg (hole B2) of ETH into the wells is insufficient to lead to inhibition of growth at the periphery, which means that the minimum inhibitory concentration is not reached with these doses. On the other hand, these doses of ETH strongly inhibit the mycobacterial growth when they are used in combination with 20 nmol of compounds of formula (I-3) (holes C1 and C2).

These results consequently demonstrate that the compounds of formula (I) in accordance with the invention make it possible to potentiate the bactericidal activity of ETH with respect to M. tuberculosis.

Example 17 In Vitro Demonstration of the Activity of the Compounds of the Invention

1) Materials and Methods

a) Measurement of the Activity of the Compounds on the Inhibition of Interaction of EthR with its Target DNA Sequence

The in vitro measurements of inhibition of binding of the EthR protein to its target DNA sequence were performed on a machine of BIAcore®2000 type (AB, Uppsala, Sweden).

The chips used are CM5 chips sold by the company GE Healthcare. Both the channels of a chip were activated with a solution containing 200 mM of EDC(N-ethyl-N′-(3-diethylaminopropyl)carbodiimide) and 50 mM of NHS (N-hydroxysuccinimide). Next, streptavidin (500 ng/μl in a solution containing 10 mM of sodium acetate (pH 3.5) was injected over 12 minutes at a flow rate of 10 μl/minute. The 106-base-pair biotinylated DNA fragment corresponding to the ethA-R intergene region was deposited on one of the two channels of the chip at a rate of 200 ng/ml in order to obtain stable binding of streptavidin corresponding to 50 RU (resonance units). This DNA fragment was obtained by PCR using the chromosomal DNA of M. tuberculosis H37Rv as matrix and O-270: 5′-CGGTCATGGATCCACGCTATCAAC-3′ (SEQ ID: No. 1) and O-271: 5′-biotin-CTGACTGGCCGCGGAGGTGGT-3′ (SEQ ID: No. 2). The second channel was functionalized with a 113-base-pair biotinylated DNA fragment (fragment +14 to +127 of the bla gene of E. coli PCR-amplified using the following oligonucleotides: O-343: 5′-TTTCCGTGTCGCCCTTATTCC-3′ (SEQ ID: No. 3) and O-344: 5′-biotin-CCACTCGTGCACCCAACTGAT-3′ (SEQ ID: No. 4).

Measurement of the binding of the EthR protein to the immobilized DNA was performed at 37° C. in a reference buffer containing 10 mM of Tris-HCl (pH=7.5), 200 mM of NaCl, 0.1 mM of EDTA, 1 mM of DTT and 1% of DMSO at a flow rate of 20 μl/minute. The specific interaction (SI) of EthR with the 106-base-pair double-stranded DNA sequence, expressed in resonance units, corresponds to the difference in signal observed between the two channels.

For each inhibition measurement, the compounds of the invention are dissolved in the reference buffer at a concentration of 3 μM. The compounds of the invention are then incubated in the presence of the protein (540 nM) at 37° C. for 5 minutes, and each solution is then injected onto the two channels of the chip for 3 minutes at a flow rate of 20 μl/minute. The inhibition values are calculated at the end of the injection according to the following equation:

${\%\mspace{14mu}{inhibition}} = {100 \times \frac{{SI}_{EthR} - {SI}_{{EthR} + {ligand}}}{{SI}_{EthR}}}$

in which SI_(EthR) corresponds to the value measured without ligand and SI_(EthR+ligand) corresponds to the value measured in the presence of to ligand.

b) In Vitro Measurement of the IC₅₀ of the Compounds of the Invention.

The IC₅₀ is the concentration needed to obtain 50% inhibition of the interaction of the EthR protein on the target DNA sequence. The in vitro measurement of this datum was performed according to the same principle as for the measurement of inhibition of the EthR/DNA binding using the BIAcore technique.

The specific interaction between EthR and the specific 106-bp DNA fragment was measured on a range of six concentrations of the compounds of the invention, this range extending from 0.11 μM to 27 μM. The IC₅₀ values are then extrapolated from the sigmoid curves obtained.

In Vitro Measurement of the MIC_(ETH) of the Compounds of the Invention on M. bovis BCG

The MIC is the minimum inhibitory concentration in μM of ethionamide (ETH) needed to inhibit the growth of mycobacteria. In the absence of the compounds of the invention, the concentration of ethionamide needed to prevent the growth of the mycobacteria is 6 μM. The minimum inhibitory concentration of ETH (MIC_(ETH)*) in the presence of a fixed concentration of compounds according to the invention (25 μM) makes it possible to evaluate the percentage of potentiation that corresponds to the following equation:

${\%\mspace{14mu}{potentiaton}} = {100 \times \frac{6}{{MIC}_{ETH}^{*}}}$

BCG 1173P2 was cultured for 10 days in Sauton medium in a cell culture flask without agitation. The culture was then diluted in fresh Sauton medium to obtain an optical density (OD) of 0.1. The culture was again diluted tenfold to obtain the working stock. Each ligand dissolved in DMSO was diluted in the inoculated culture medium to obtain a final concentration of 25 μM (DMSO 0.5% final). These solutions were then used to inoculate the BCG cultures in the presence of ethionamide solutions of increasing concentrations ranging from 0.04 μg/ml to 5 μg/mL. The tubes were then incubated with agitation at 37° C. The OD of the tubes was taken each day for 10 days by reading through the tube. The MIC corresponds to the minimum concentration of ethionamide that enables the bacterial growth to be inhibited and thus for which the OD remains unchanged.

d) Potentiating Effect of the Compounds of the Invention on M. tuberculosis H37Rv

The ethionamide-potentiating effect of certain compounds of the invention was evaluated using:

-   -   either the RIA detection method in liquid medium on a Bactec®         460 robot in 12 B medium,     -   or the fluorimetric detection method in liquid medium on a         Bactec® MG IT 960 robot.

i) RIA detection method on Bactec® 460.

The Bactec® system (Becton Dickinson) is based on a radiometric respirometry method. It consists in assessing the growth of the mycobacteria by measuring the amount of ¹⁴CO₂ released by the mycobacteria during their growth in a culture medium containing ¹⁴C-labeled palmitic acid as sole carbon source. The machine enables measurement of the amount of ¹⁴CO₂ in the gaseous atmosphere of the flask and to express it according to a graduation known as the GI (Growth Index) ranging from 0 (absence of ¹⁴CO₂) to 999, corresponding to the maximum amount of growth that can be detected by the robot.

The reference strain M. tuberculosis H37Rv was maintained in Jensen medium. A suspension in sterile distilled water served to inject 12B medium, and incubated in the Bactec® 460 system until a GI=500 was obtained. A hundred-fold dilution was performed and 100 μl were injected into the Bactec® 12B flasks. When the flask reached a growth index of greater than 300, the compounds of the invention were added at a final concentration of 25 or 100 mM against a concentration range of ethionamide extending from 6 to 0.06 mM. A control series containing ethionamide alone, or the compounds of the invention alone, was prepared. The flasks were incubated at 37° C. and a respirometric reading was taken once a day from D+1 up to D+9.

The GI value measurements were used to determine the potentiating effect of the compounds according to the invention. Only the maximum concentration value of the compounds of the invention (25 or 100 μM) not affecting the value of GI in the absence of ETH was considered to determine the potentiating effect. Potentiation is acknowledged if the minimum inhibitory concentration of ETH is reduced at least twofold by the presence of a compound of the invention, and if said compound has no effect alone on the growth at that same concentration.

ii) Fluorimetric detection method in liquid medium on the Bactec° MG IT 960 robot.

This method uses a ruthenium salt, this substance emitting fluorescence that is proportionately stronger the lower the partial pressure of oxygen. The metabolism of the mycobacteria causes a depletion of oxygen and results in the appearance of fluorescence whose intensity is proportional to the level of reduction of the medium.

The M. tuberculosis H37RV mycobacterial strain was prepared as described previously and inoculated in MGIT tubes. An ethionamide concentration range extending from 6 to 0.6 mM was added to a series of tubes containing the test compounds of the invention (either 25 or 100 μM) and to a series containing no compound. The positive control comprised only the mycobacteria inoculated in the medium. The fluorescence readings were taken daily up to a maximum of nine days.

The fluorescence value measurements were used to determine the potentiating effect of the compounds according to the invention. Only the maximum concentration value of the compounds of the invention (25 or 100 μM) not affecting the fluorescence value in the absence of ETH was considered to determine the potentiating effect. Potentiation is acknowledged if the minimum inhibitory concentration of ETH is reduced at least twofold by the presence of a compound of the invention, and if said compound has no effect alone on the growth at that same concentration.

e) Measurement of the Solubility of the Compounds of the Invention

40 μl of a solution containing a compound of the invention at a concentration of 10 mM in DMSO were diluted in 1.960 ml of methanol, and another 40 μl were diluted in 1.960 ml of a PBS solution containing 675 mM of NaCl, 13.5 mM of KCl, 50 mM of Na₂HPO₄.2H₂O and 10 mM of KH₂PO₄ at a pH of 7.4. The two solutions were stirred for 24 hours at room temperature, and then centrifuged for 5 minutes and filtered through 0.45 μm filters. 20 μl of each solution were then diluted in 118 μl of methanol and analyzed by liquid chromatography coupled to mass spectrometry (LC/MS). The solubility was determined by the ratio of the areas under the curve of the mass signal for the compound of the invention, according to the following equation:

${solubility} = \frac{{Area}_{PBS}}{{Area}_{methanol}}$

2) Results

The results obtained as regards the inhibition of interaction of EthR with its target DNA sequence, the IC₅₀, the MIC_(ETH) and the potentiating effect of the compounds of the invention on ethionamide activity are collated in Table I below:

TABLE I Compound No. Inhibition % IC₅₀ (μM) MIC_(ETH) (μM) Potentiation % I-1 33 1.54 0.24 2500  3 14 ND 1.20 500 4 15 ND 1.20 500 5 15 ND ND ND 12 19 ND 1.20 ND 15 94 1.56 ND ND 16   15^(a) 38.0^(b) 1.20 500 19 15 ND ND ND 20 53 1 0.24 2500  21 20 ND 1.2  500 22 28 3.33 0.24 2500  25 70 0.91 1.2  500 27 96 1.57 1.2  500 33 71 1.12 0.24 2500  34 48 ND ND ND 35 52 1.49 0.24 2500  36 78 1 1.2  500 37 76 3.49 ND ND 40 59 ND ND ND 41 45 ND 0.24 ND 43 93 0.52 0.24 2500  44 96 0.95 ND ND 45 75 1.5 0.24 2500  46 100^(a), 52^(c) 1.79 1.20 500 47 100^(a), 28^(c) 15.2 ND ND 48 56 1.14 ND ND 49 86 1.34 ND ND 50 96 0.44 ND ND 51 13 ND ND ND 52 61 ND ND ND 53 34 ND ND ND 54  5 ND ND ND 55 100  0.908 1.20 500 56 100  0.944 0.24 2500  57 46 ND ND ND 58 34 ND ND ND 59 77 0.39 ND ND ^(a)DNA test conditions: 20 RU, EthR: 200 nM, compound: 25 μM. ^(c)DNA test conditions: 20 RU, EthR: 350 nM ^(c)DNA test conditions: 20 RU, EthR: 200 nM, compound: 1 μM. under these conditions, the reference compound (I-1) had a percentage of inhibition equal to 45%.

The ethionamide-potentiating effect of compound (I-1) evaluated according to the RIA detection method in liquid medium on the Bactec® 460 robot in 12 B medium is shown in the attached FIG. 2, in which the growth index (arbitrary units) is presented as a function of the time in days. The key to this figure is as follows:

-   -   broken line, filled circles: compound (I-1) alone 25 μM;     -   continuous line, empty triangles: ETH 0.5 μg/ml;     -   broken line, filled triangles: ETH 0.1 μg/ml+compound (I-1) 25         μM;     -   continuous line, filled circles: ETH 1 μg/ml;     -   continuous line, filled squares: ETH 0.25 μg/ml;     -   continuous line, filled triangles: negative control without any         chemical compound.

The results presented in this figure indicate that the MIC for ETH under these experimental conditions is 1 μg/ml (6 μM) (curve with the filled squares). The same growth-inhibiting effect is obtained by placing in contact 0.1 μg/ml (0.6 μM) of ETH and 25 μM of compound (I-1). The potentiating effect of compound (I-1) of the invention is thus at least equal to a factor of 10.

The activity of compounds 33 and 43 of the invention was also evaluated in vitro at 25 μM on the Bactec® 960 machine

Compounds 33 and 43 were tested as regards their capacity to potentiate ethionamide (ETH) with the Bactec® MGIT 960 machine, according to the procedure described above.

The results obtained are presented in Table II below:

TABLE II Tube Strain [ETH] (μg/mL) Ligand 25 μM D + 0 D + 1 D + 5 D + 5 D + 6 D + 7 D + 7 J + 8 State A1  1% 0 0 0 0 0 0 0 78 151 400 C A2  1% solvent 0 0 0 0 0 0 110 199 400 R A3  1% 0 Compound 33 0 0 0 0 1 180 319 400 R A4 100% solvent 0 0 0 400 400 400 400 400 400 R A5 100% 0 Compound 33 0 0 400 400 400 400 400 400 R B1  1% 0 0 0 0 0 0 0 149 262 400 C B2 100% 2 0 0 0 0 0 0 0 0 0 S B3 100% 1 0 0 0 0 0 0 0 0 0 S B4 100% 0.5 0 0 0 0 0 0 6 16 23 S B5 100% 0.25 0 0 0 14 36 125 400 400 400 R C1  1% 0 0 0 0 0 0 0 194 329 400 C C2 100% 0.25 Compound 33 0 0 0 0 0 0 0 0 S C3 100% 0.1 Compound 33 0 0 0 0 0 0 0 0 S C4 100% 0.05 Compound 33 0 0 0 0 0 0 0 0 S C5 100% 0.025 Compound 33 0 0 200 353 400 400 400 400 R D1  1% 0 0 0 0 0 0 0 42 96 400 C D2  1% 0 Compound 43 0 0 0 0 0 168 292 400 R D3 100% 0 Compound 43 0 0 400 400 400 400 400 400 R E1  1% 0 0 0 0 0 0 0 80 150 400 C E2 100% 0.25 Compound 43 0 0 0 0 0 0 0 0 S E3 100% 0.1 Compound 43 0 0 0 0 0 0 0 0 S E4 100% 0.05 Compound 43 0 0 0 0 0 0 0 0 S E5 100% 0.025 Compound 43 0 0 0 0 0 0 0 0 S Key: C = control; S = sensitive (total inhibition of bacterial growth); R = resistant (appearance of bacterial growth)

It may be observed that the measurements performed in the presence of compounds 33 and 43 reveal the absence of bacterial growth-inhibiting properties of these compounds at 25 μM (Table II: lines A5 and D3).

This table also gives information regarding the MIC of ethionamide used as sole growth inhibitor (lines B1 to B5). This is equal to 1 μg/ml (6 μM) under the experimental conditions. The ETH-potentiating effect of compound 33 is illustrated by the measurements taken at C1 to C5, which indicate that, in the presence of compound 33 of the invention, the MIC for ETH falls to 0.05 μg/ml (0.3 μM), i.e. a factor of 20. As regards compound 43 of the invention, lines E1 to E5 reveal that the MIC for ETH in the presence of this compound is less than 0.025 μg/mL (0.15 μM). Compound 43 of the invention allows potentiation of the ethionamide activity by a factor at least equal to 40.

Compounds 20 and 22 showed ETH-activity potentiation of a factor of about 20 and 10, respectively, in this same test.

Solubility Results for Certain Compounds of the Invention:

The solubility of certain compounds of the invention tested under the conditions detailed above is given in Table III below:

TABLE III Compound No. Solubility (μg/mL) 1 9.5 5 9 12 71 17 55.5 20 63.5 22 60.4 28 61.5 31 67.1 33 63.5 43 26.9 44 16.3 46 53.7 48 0.86 50 2.9 51 271.73 54 38.7 

1. A pharmaceutical composition comprising as active principle at least one compound of formula (I-e), at least one pharmaceutically acceptable excipient and at least one antibiotic that is activatable via the EthA enzymatic pathway, wherein the compounds corresponding to formula (I-e) are as follows:

in which X₂ is chosen from the groups (X₂-1) to (X₂-23) below:


2. The composition as claimed in claim 1, wherein the antibiotic is chosen from ethionamide, prothionamide, isoxyl and thiacetazone.
 3. A product containing at least one compound of formula (I-e) as defined in claim 1, and at least one antibiotic chosen from antibiotics that are activatable via the EthA enzymatic pathway, as combination products for simultaneous, separate or sequential use over time in general anti-tuberculous, anti-lepromatous or anti-mycobacterial therapy.
 4. A product containing at least one compound of formula (I-e) as defined in claim 1 and at least one antibiotic chosen from ethionamide, prothionamide, isoxyl and thiacetazone, as combination products for simultaneous, separate or sequential use over time in general anti-tuberculous, anti-lepromatous or anti-mycobacterial therapy.
 5. A medicament comprising the compounds of formula (I-e) as defined in claim
 1. 6. A pharmaceutical composition comprising, as active principle, at least one compound of formula (I-e) as defined in claim 1, and at least one pharmaceutically acceptable excipient.
 7. Compounds corresponding to formula (I-e) as follows:

in which X₂ is chosen from the groups (X₂-1) to (X₂-23) below:


8. The compounds of claim 7 wherein the compounds are selected from the group consisting of: 2-azido-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone; 4-iodo-N-(1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-1,2,3-triazol-4-ylmethyl)benzenesulfonamide; 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5yl)piperid-1-yl]-2-[1,2,3]triazol-1-ylethanone of formula (I-8) below:

2-(2,2,2-trifluoroacetyl)-1,2,3,4-tetrahydroisoquinoline-7-sulfonic acid (1-{2-oxo-2-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethyl}-1H-[1,2,3]triazol-4-ylmethyl)amide of formula (I-9) below:

2-phenoxy-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 3-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propan-1-one; 2-thiophen-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 4-methyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pentan-1-one; 2-bicyclo[2.2.1]hept-2-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; -2-cyclopropyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; and 2-phenyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone.
 9. The compounds of claim 7 wherein the compounds are selected from the group consisting of: 2-cyclohexyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 2-cyclopent-2-enyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 2-cyclopentyl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; 4,4,4-trifluoro-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]butan-1-one; 1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]pent-4-yn-1-one; 3-oxo-3-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]propionitrile; 2-thiophen-3-yl-1-[4-(3-thiophen-2-yl[1,2,4]oxadiozal-5-yl)piperid-1-yl]ethanone; 2-(2-aminothiazol-4-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone; and 2-(1H-tetrazol-5-yl)-1-[4-(3-thiophen-2-yl[1,2,4]oxadiazol-5-yl)piperid-1-yl]ethanone. 